--- /dev/null
+/*
+ * Generic ring buffer
+ *
+ * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
+ */
+#include <linux/ftrace_event.h>
+#include <linux/ring_buffer.h>
+#include <linux/trace_clock.h>
+#include <linux/trace_seq.h>
+#include <linux/spinlock.h>
+#include <linux/irq_work.h>
+#include <linux/uaccess.h>
+#include <linux/hardirq.h>
+#include <linux/kthread.h> /* for self test */
+#include <linux/kmemcheck.h>
+#include <linux/module.h>
+#include <linux/percpu.h>
+#include <linux/mutex.h>
+#include <linux/delay.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/hash.h>
+#include <linux/list.h>
+#include <linux/cpu.h>
+
+#include <asm/local.h>
+
+static void update_pages_handler(struct work_struct *work);
+
+/*
+ * The ring buffer header is special. We must manually up keep it.
+ */
+int ring_buffer_print_entry_header(struct trace_seq *s)
+{
+ trace_seq_puts(s, "# compressed entry header\n");
+ trace_seq_puts(s, "\ttype_len : 5 bits\n");
+ trace_seq_puts(s, "\ttime_delta : 27 bits\n");
+ trace_seq_puts(s, "\tarray : 32 bits\n");
+ trace_seq_putc(s, '\n');
+ trace_seq_printf(s, "\tpadding : type == %d\n",
+ RINGBUF_TYPE_PADDING);
+ trace_seq_printf(s, "\ttime_extend : type == %d\n",
+ RINGBUF_TYPE_TIME_EXTEND);
+ trace_seq_printf(s, "\tdata max type_len == %d\n",
+ RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
+
+ return !trace_seq_has_overflowed(s);
+}
+
+/*
+ * The ring buffer is made up of a list of pages. A separate list of pages is
+ * allocated for each CPU. A writer may only write to a buffer that is
+ * associated with the CPU it is currently executing on. A reader may read
+ * from any per cpu buffer.
+ *
+ * The reader is special. For each per cpu buffer, the reader has its own
+ * reader page. When a reader has read the entire reader page, this reader
+ * page is swapped with another page in the ring buffer.
+ *
+ * Now, as long as the writer is off the reader page, the reader can do what
+ * ever it wants with that page. The writer will never write to that page
+ * again (as long as it is out of the ring buffer).
+ *
+ * Here's some silly ASCII art.
+ *
+ * +------+
+ * |reader| RING BUFFER
+ * |page |
+ * +------+ +---+ +---+ +---+
+ * | |-->| |-->| |
+ * +---+ +---+ +---+
+ * ^ |
+ * | |
+ * +---------------+
+ *
+ *
+ * +------+
+ * |reader| RING BUFFER
+ * |page |------------------v
+ * +------+ +---+ +---+ +---+
+ * | |-->| |-->| |
+ * +---+ +---+ +---+
+ * ^ |
+ * | |
+ * +---------------+
+ *
+ *
+ * +------+
+ * |reader| RING BUFFER
+ * |page |------------------v
+ * +------+ +---+ +---+ +---+
+ * ^ | |-->| |-->| |
+ * | +---+ +---+ +---+
+ * | |
+ * | |
+ * +------------------------------+
+ *
+ *
+ * +------+
+ * |buffer| RING BUFFER
+ * |page |------------------v
+ * +------+ +---+ +---+ +---+
+ * ^ | | | |-->| |
+ * | New +---+ +---+ +---+
+ * | Reader------^ |
+ * | page |
+ * +------------------------------+
+ *
+ *
+ * After we make this swap, the reader can hand this page off to the splice
+ * code and be done with it. It can even allocate a new page if it needs to
+ * and swap that into the ring buffer.
+ *
+ * We will be using cmpxchg soon to make all this lockless.
+ *
+ */
+
+/*
+ * A fast way to enable or disable all ring buffers is to
+ * call tracing_on or tracing_off. Turning off the ring buffers
+ * prevents all ring buffers from being recorded to.
+ * Turning this switch on, makes it OK to write to the
+ * ring buffer, if the ring buffer is enabled itself.
+ *
+ * There's three layers that must be on in order to write
+ * to the ring buffer.
+ *
+ * 1) This global flag must be set.
+ * 2) The ring buffer must be enabled for recording.
+ * 3) The per cpu buffer must be enabled for recording.
+ *
+ * In case of an anomaly, this global flag has a bit set that
+ * will permantly disable all ring buffers.
+ */
+
+/*
+ * Global flag to disable all recording to ring buffers
+ * This has two bits: ON, DISABLED
+ *
+ * ON DISABLED
+ * ---- ----------
+ * 0 0 : ring buffers are off
+ * 1 0 : ring buffers are on
+ * X 1 : ring buffers are permanently disabled
+ */
+
+enum {
+ RB_BUFFERS_ON_BIT = 0,
+ RB_BUFFERS_DISABLED_BIT = 1,
+};
+
+enum {
+ RB_BUFFERS_ON = 1 << RB_BUFFERS_ON_BIT,
+ RB_BUFFERS_DISABLED = 1 << RB_BUFFERS_DISABLED_BIT,
+};
+
+static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON;
+
+/* Used for individual buffers (after the counter) */
+#define RB_BUFFER_OFF (1 << 20)
+
+#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
+
+/**
+ * tracing_off_permanent - permanently disable ring buffers
+ *
+ * This function, once called, will disable all ring buffers
+ * permanently.
+ */
+void tracing_off_permanent(void)
+{
+ set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags);
+}
+
+#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
+#define RB_ALIGNMENT 4U
+#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
+#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
+
+#ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
+# define RB_FORCE_8BYTE_ALIGNMENT 0
+# define RB_ARCH_ALIGNMENT RB_ALIGNMENT
+#else
+# define RB_FORCE_8BYTE_ALIGNMENT 1
+# define RB_ARCH_ALIGNMENT 8U
+#endif
+
+#define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
+
+/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
+#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
+
+enum {
+ RB_LEN_TIME_EXTEND = 8,
+ RB_LEN_TIME_STAMP = 16,
+};
+
+#define skip_time_extend(event) \
+ ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
+
+static inline int rb_null_event(struct ring_buffer_event *event)
+{
+ return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
+}
+
+static void rb_event_set_padding(struct ring_buffer_event *event)
+{
+ /* padding has a NULL time_delta */
+ event->type_len = RINGBUF_TYPE_PADDING;
+ event->time_delta = 0;
+}
+
+static unsigned
+rb_event_data_length(struct ring_buffer_event *event)
+{
+ unsigned length;
+
+ if (event->type_len)
+ length = event->type_len * RB_ALIGNMENT;
+ else
+ length = event->array[0];
+ return length + RB_EVNT_HDR_SIZE;
+}
+
+/*
+ * Return the length of the given event. Will return
+ * the length of the time extend if the event is a
+ * time extend.
+ */
+static inline unsigned
+rb_event_length(struct ring_buffer_event *event)
+{
+ switch (event->type_len) {
+ case RINGBUF_TYPE_PADDING:
+ if (rb_null_event(event))
+ /* undefined */
+ return -1;
+ return event->array[0] + RB_EVNT_HDR_SIZE;
+
+ case RINGBUF_TYPE_TIME_EXTEND:
+ return RB_LEN_TIME_EXTEND;
+
+ case RINGBUF_TYPE_TIME_STAMP:
+ return RB_LEN_TIME_STAMP;
+
+ case RINGBUF_TYPE_DATA:
+ return rb_event_data_length(event);
+ default:
+ BUG();
+ }
+ /* not hit */
+ return 0;
+}
+
+/*
+ * Return total length of time extend and data,
+ * or just the event length for all other events.
+ */
+static inline unsigned
+rb_event_ts_length(struct ring_buffer_event *event)
+{
+ unsigned len = 0;
+
+ if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
+ /* time extends include the data event after it */
+ len = RB_LEN_TIME_EXTEND;
+ event = skip_time_extend(event);
+ }
+ return len + rb_event_length(event);
+}
+
+/**
+ * ring_buffer_event_length - return the length of the event
+ * @event: the event to get the length of
+ *
+ * Returns the size of the data load of a data event.
+ * If the event is something other than a data event, it
+ * returns the size of the event itself. With the exception
+ * of a TIME EXTEND, where it still returns the size of the
+ * data load of the data event after it.
+ */
+unsigned ring_buffer_event_length(struct ring_buffer_event *event)
+{
+ unsigned length;
+
+ if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
+ event = skip_time_extend(event);
+
+ length = rb_event_length(event);
+ if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
+ return length;
+ length -= RB_EVNT_HDR_SIZE;
+ if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
+ length -= sizeof(event->array[0]);
+ return length;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_event_length);
+
+/* inline for ring buffer fast paths */
+static void *
+rb_event_data(struct ring_buffer_event *event)
+{
+ if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
+ event = skip_time_extend(event);
+ BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
+ /* If length is in len field, then array[0] has the data */
+ if (event->type_len)
+ return (void *)&event->array[0];
+ /* Otherwise length is in array[0] and array[1] has the data */
+ return (void *)&event->array[1];
+}
+
+/**
+ * ring_buffer_event_data - return the data of the event
+ * @event: the event to get the data from
+ */
+void *ring_buffer_event_data(struct ring_buffer_event *event)
+{
+ return rb_event_data(event);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_event_data);
+
+#define for_each_buffer_cpu(buffer, cpu) \
+ for_each_cpu(cpu, buffer->cpumask)
+
+#define TS_SHIFT 27
+#define TS_MASK ((1ULL << TS_SHIFT) - 1)
+#define TS_DELTA_TEST (~TS_MASK)
+
+/* Flag when events were overwritten */
+#define RB_MISSED_EVENTS (1 << 31)
+/* Missed count stored at end */
+#define RB_MISSED_STORED (1 << 30)
+
+struct buffer_data_page {
+ u64 time_stamp; /* page time stamp */
+ local_t commit; /* write committed index */
+ unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
+};
+
+/*
+ * Note, the buffer_page list must be first. The buffer pages
+ * are allocated in cache lines, which means that each buffer
+ * page will be at the beginning of a cache line, and thus
+ * the least significant bits will be zero. We use this to
+ * add flags in the list struct pointers, to make the ring buffer
+ * lockless.
+ */
+struct buffer_page {
+ struct list_head list; /* list of buffer pages */
+ local_t write; /* index for next write */
+ unsigned read; /* index for next read */
+ local_t entries; /* entries on this page */
+ unsigned long real_end; /* real end of data */
+ struct buffer_data_page *page; /* Actual data page */
+};
+
+/*
+ * The buffer page counters, write and entries, must be reset
+ * atomically when crossing page boundaries. To synchronize this
+ * update, two counters are inserted into the number. One is
+ * the actual counter for the write position or count on the page.
+ *
+ * The other is a counter of updaters. Before an update happens
+ * the update partition of the counter is incremented. This will
+ * allow the updater to update the counter atomically.
+ *
+ * The counter is 20 bits, and the state data is 12.
+ */
+#define RB_WRITE_MASK 0xfffff
+#define RB_WRITE_INTCNT (1 << 20)
+
+static void rb_init_page(struct buffer_data_page *bpage)
+{
+ local_set(&bpage->commit, 0);
+}
+
+/**
+ * ring_buffer_page_len - the size of data on the page.
+ * @page: The page to read
+ *
+ * Returns the amount of data on the page, including buffer page header.
+ */
+size_t ring_buffer_page_len(void *page)
+{
+ return local_read(&((struct buffer_data_page *)page)->commit)
+ + BUF_PAGE_HDR_SIZE;
+}
+
+/*
+ * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
+ * this issue out.
+ */
+static void free_buffer_page(struct buffer_page *bpage)
+{
+ free_page((unsigned long)bpage->page);
+ kfree(bpage);
+}
+
+/*
+ * We need to fit the time_stamp delta into 27 bits.
+ */
+static inline int test_time_stamp(u64 delta)
+{
+ if (delta & TS_DELTA_TEST)
+ return 1;
+ return 0;
+}
+
+#define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
+
+/* Max payload is BUF_PAGE_SIZE - header (8bytes) */
+#define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
+
+int ring_buffer_print_page_header(struct trace_seq *s)
+{
+ struct buffer_data_page field;
+
+ trace_seq_printf(s, "\tfield: u64 timestamp;\t"
+ "offset:0;\tsize:%u;\tsigned:%u;\n",
+ (unsigned int)sizeof(field.time_stamp),
+ (unsigned int)is_signed_type(u64));
+
+ trace_seq_printf(s, "\tfield: local_t commit;\t"
+ "offset:%u;\tsize:%u;\tsigned:%u;\n",
+ (unsigned int)offsetof(typeof(field), commit),
+ (unsigned int)sizeof(field.commit),
+ (unsigned int)is_signed_type(long));
+
+ trace_seq_printf(s, "\tfield: int overwrite;\t"
+ "offset:%u;\tsize:%u;\tsigned:%u;\n",
+ (unsigned int)offsetof(typeof(field), commit),
+ 1,
+ (unsigned int)is_signed_type(long));
+
+ trace_seq_printf(s, "\tfield: char data;\t"
+ "offset:%u;\tsize:%u;\tsigned:%u;\n",
+ (unsigned int)offsetof(typeof(field), data),
+ (unsigned int)BUF_PAGE_SIZE,
+ (unsigned int)is_signed_type(char));
+
+ return !trace_seq_has_overflowed(s);
+}
+
+struct rb_irq_work {
+ struct irq_work work;
+ wait_queue_head_t waiters;
+ wait_queue_head_t full_waiters;
+ bool waiters_pending;
+ bool full_waiters_pending;
+ bool wakeup_full;
+};
+
+/*
+ * head_page == tail_page && head == tail then buffer is empty.
+ */
+struct ring_buffer_per_cpu {
+ int cpu;
+ atomic_t record_disabled;
+ struct ring_buffer *buffer;
+ raw_spinlock_t reader_lock; /* serialize readers */
+ arch_spinlock_t lock;
+ struct lock_class_key lock_key;
+ unsigned int nr_pages;
+ struct list_head *pages;
+ struct buffer_page *head_page; /* read from head */
+ struct buffer_page *tail_page; /* write to tail */
+ struct buffer_page *commit_page; /* committed pages */
+ struct buffer_page *reader_page;
+ unsigned long lost_events;
+ unsigned long last_overrun;
+ local_t entries_bytes;
+ local_t entries;
+ local_t overrun;
+ local_t commit_overrun;
+ local_t dropped_events;
+ local_t committing;
+ local_t commits;
+ unsigned long read;
+ unsigned long read_bytes;
+ u64 write_stamp;
+ u64 read_stamp;
+ /* ring buffer pages to update, > 0 to add, < 0 to remove */
+ int nr_pages_to_update;
+ struct list_head new_pages; /* new pages to add */
+ struct work_struct update_pages_work;
+ struct completion update_done;
+
+ struct rb_irq_work irq_work;
+};
+
+struct ring_buffer {
+ unsigned flags;
+ int cpus;
+ atomic_t record_disabled;
+ atomic_t resize_disabled;
+ cpumask_var_t cpumask;
+
+ struct lock_class_key *reader_lock_key;
+
+ struct mutex mutex;
+
+ struct ring_buffer_per_cpu **buffers;
+
+#ifdef CONFIG_HOTPLUG_CPU
+ struct notifier_block cpu_notify;
+#endif
+ u64 (*clock)(void);
+
+ struct rb_irq_work irq_work;
+};
+
+struct ring_buffer_iter {
+ struct ring_buffer_per_cpu *cpu_buffer;
+ unsigned long head;
+ struct buffer_page *head_page;
+ struct buffer_page *cache_reader_page;
+ unsigned long cache_read;
+ u64 read_stamp;
+};
+
+/*
+ * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
+ *
+ * Schedules a delayed work to wake up any task that is blocked on the
+ * ring buffer waiters queue.
+ */
+static void rb_wake_up_waiters(struct irq_work *work)
+{
+ struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
+
+ wake_up_all(&rbwork->waiters);
+ if (rbwork->wakeup_full) {
+ rbwork->wakeup_full = false;
+ wake_up_all(&rbwork->full_waiters);
+ }
+}
+
+/**
+ * ring_buffer_wait - wait for input to the ring buffer
+ * @buffer: buffer to wait on
+ * @cpu: the cpu buffer to wait on
+ * @full: wait until a full page is available, if @cpu != RING_BUFFER_ALL_CPUS
+ *
+ * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
+ * as data is added to any of the @buffer's cpu buffers. Otherwise
+ * it will wait for data to be added to a specific cpu buffer.
+ */
+int ring_buffer_wait(struct ring_buffer *buffer, int cpu, bool full)
+{
+ struct ring_buffer_per_cpu *uninitialized_var(cpu_buffer);
+ DEFINE_WAIT(wait);
+ struct rb_irq_work *work;
+ int ret = 0;
+
+ /*
+ * Depending on what the caller is waiting for, either any
+ * data in any cpu buffer, or a specific buffer, put the
+ * caller on the appropriate wait queue.
+ */
+ if (cpu == RING_BUFFER_ALL_CPUS) {
+ work = &buffer->irq_work;
+ /* Full only makes sense on per cpu reads */
+ full = false;
+ } else {
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ return -ENODEV;
+ cpu_buffer = buffer->buffers[cpu];
+ work = &cpu_buffer->irq_work;
+ }
+
+
+ while (true) {
+ if (full)
+ prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE);
+ else
+ prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE);
+
+ /*
+ * The events can happen in critical sections where
+ * checking a work queue can cause deadlocks.
+ * After adding a task to the queue, this flag is set
+ * only to notify events to try to wake up the queue
+ * using irq_work.
+ *
+ * We don't clear it even if the buffer is no longer
+ * empty. The flag only causes the next event to run
+ * irq_work to do the work queue wake up. The worse
+ * that can happen if we race with !trace_empty() is that
+ * an event will cause an irq_work to try to wake up
+ * an empty queue.
+ *
+ * There's no reason to protect this flag either, as
+ * the work queue and irq_work logic will do the necessary
+ * synchronization for the wake ups. The only thing
+ * that is necessary is that the wake up happens after
+ * a task has been queued. It's OK for spurious wake ups.
+ */
+ if (full)
+ work->full_waiters_pending = true;
+ else
+ work->waiters_pending = true;
+
+ if (signal_pending(current)) {
+ ret = -EINTR;
+ break;
+ }
+
+ if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer))
+ break;
+
+ if (cpu != RING_BUFFER_ALL_CPUS &&
+ !ring_buffer_empty_cpu(buffer, cpu)) {
+ unsigned long flags;
+ bool pagebusy;
+
+ if (!full)
+ break;
+
+ raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+ pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
+ raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+
+ if (!pagebusy)
+ break;
+ }
+
+ schedule();
+ }
+
+ if (full)
+ finish_wait(&work->full_waiters, &wait);
+ else
+ finish_wait(&work->waiters, &wait);
+
+ return ret;
+}
+
+/**
+ * ring_buffer_poll_wait - poll on buffer input
+ * @buffer: buffer to wait on
+ * @cpu: the cpu buffer to wait on
+ * @filp: the file descriptor
+ * @poll_table: The poll descriptor
+ *
+ * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
+ * as data is added to any of the @buffer's cpu buffers. Otherwise
+ * it will wait for data to be added to a specific cpu buffer.
+ *
+ * Returns POLLIN | POLLRDNORM if data exists in the buffers,
+ * zero otherwise.
+ */
+int ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu,
+ struct file *filp, poll_table *poll_table)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ struct rb_irq_work *work;
+
+ if (cpu == RING_BUFFER_ALL_CPUS)
+ work = &buffer->irq_work;
+ else {
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ return -EINVAL;
+
+ cpu_buffer = buffer->buffers[cpu];
+ work = &cpu_buffer->irq_work;
+ }
+
+ poll_wait(filp, &work->waiters, poll_table);
+ work->waiters_pending = true;
+ /*
+ * There's a tight race between setting the waiters_pending and
+ * checking if the ring buffer is empty. Once the waiters_pending bit
+ * is set, the next event will wake the task up, but we can get stuck
+ * if there's only a single event in.
+ *
+ * FIXME: Ideally, we need a memory barrier on the writer side as well,
+ * but adding a memory barrier to all events will cause too much of a
+ * performance hit in the fast path. We only need a memory barrier when
+ * the buffer goes from empty to having content. But as this race is
+ * extremely small, and it's not a problem if another event comes in, we
+ * will fix it later.
+ */
+ smp_mb();
+
+ if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
+ (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
+ return POLLIN | POLLRDNORM;
+ return 0;
+}
+
+/* buffer may be either ring_buffer or ring_buffer_per_cpu */
+#define RB_WARN_ON(b, cond) \
+ ({ \
+ int _____ret = unlikely(cond); \
+ if (_____ret) { \
+ if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
+ struct ring_buffer_per_cpu *__b = \
+ (void *)b; \
+ atomic_inc(&__b->buffer->record_disabled); \
+ } else \
+ atomic_inc(&b->record_disabled); \
+ WARN_ON(1); \
+ } \
+ _____ret; \
+ })
+
+/* Up this if you want to test the TIME_EXTENTS and normalization */
+#define DEBUG_SHIFT 0
+
+static inline u64 rb_time_stamp(struct ring_buffer *buffer)
+{
+ /* shift to debug/test normalization and TIME_EXTENTS */
+ return buffer->clock() << DEBUG_SHIFT;
+}
+
+u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
+{
+ u64 time;
+
+ preempt_disable_notrace();
+ time = rb_time_stamp(buffer);
+ preempt_enable_no_resched_notrace();
+
+ return time;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
+
+void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
+ int cpu, u64 *ts)
+{
+ /* Just stupid testing the normalize function and deltas */
+ *ts >>= DEBUG_SHIFT;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
+
+/*
+ * Making the ring buffer lockless makes things tricky.
+ * Although writes only happen on the CPU that they are on,
+ * and they only need to worry about interrupts. Reads can
+ * happen on any CPU.
+ *
+ * The reader page is always off the ring buffer, but when the
+ * reader finishes with a page, it needs to swap its page with
+ * a new one from the buffer. The reader needs to take from
+ * the head (writes go to the tail). But if a writer is in overwrite
+ * mode and wraps, it must push the head page forward.
+ *
+ * Here lies the problem.
+ *
+ * The reader must be careful to replace only the head page, and
+ * not another one. As described at the top of the file in the
+ * ASCII art, the reader sets its old page to point to the next
+ * page after head. It then sets the page after head to point to
+ * the old reader page. But if the writer moves the head page
+ * during this operation, the reader could end up with the tail.
+ *
+ * We use cmpxchg to help prevent this race. We also do something
+ * special with the page before head. We set the LSB to 1.
+ *
+ * When the writer must push the page forward, it will clear the
+ * bit that points to the head page, move the head, and then set
+ * the bit that points to the new head page.
+ *
+ * We also don't want an interrupt coming in and moving the head
+ * page on another writer. Thus we use the second LSB to catch
+ * that too. Thus:
+ *
+ * head->list->prev->next bit 1 bit 0
+ * ------- -------
+ * Normal page 0 0
+ * Points to head page 0 1
+ * New head page 1 0
+ *
+ * Note we can not trust the prev pointer of the head page, because:
+ *
+ * +----+ +-----+ +-----+
+ * | |------>| T |---X--->| N |
+ * | |<------| | | |
+ * +----+ +-----+ +-----+
+ * ^ ^ |
+ * | +-----+ | |
+ * +----------| R |----------+ |
+ * | |<-----------+
+ * +-----+
+ *
+ * Key: ---X--> HEAD flag set in pointer
+ * T Tail page
+ * R Reader page
+ * N Next page
+ *
+ * (see __rb_reserve_next() to see where this happens)
+ *
+ * What the above shows is that the reader just swapped out
+ * the reader page with a page in the buffer, but before it
+ * could make the new header point back to the new page added
+ * it was preempted by a writer. The writer moved forward onto
+ * the new page added by the reader and is about to move forward
+ * again.
+ *
+ * You can see, it is legitimate for the previous pointer of
+ * the head (or any page) not to point back to itself. But only
+ * temporarially.
+ */
+
+#define RB_PAGE_NORMAL 0UL
+#define RB_PAGE_HEAD 1UL
+#define RB_PAGE_UPDATE 2UL
+
+
+#define RB_FLAG_MASK 3UL
+
+/* PAGE_MOVED is not part of the mask */
+#define RB_PAGE_MOVED 4UL
+
+/*
+ * rb_list_head - remove any bit
+ */
+static struct list_head *rb_list_head(struct list_head *list)
+{
+ unsigned long val = (unsigned long)list;
+
+ return (struct list_head *)(val & ~RB_FLAG_MASK);
+}
+
+/*
+ * rb_is_head_page - test if the given page is the head page
+ *
+ * Because the reader may move the head_page pointer, we can
+ * not trust what the head page is (it may be pointing to
+ * the reader page). But if the next page is a header page,
+ * its flags will be non zero.
+ */
+static inline int
+rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer,
+ struct buffer_page *page, struct list_head *list)
+{
+ unsigned long val;
+
+ val = (unsigned long)list->next;
+
+ if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
+ return RB_PAGE_MOVED;
+
+ return val & RB_FLAG_MASK;
+}
+
+/*
+ * rb_is_reader_page
+ *
+ * The unique thing about the reader page, is that, if the
+ * writer is ever on it, the previous pointer never points
+ * back to the reader page.
+ */
+static int rb_is_reader_page(struct buffer_page *page)
+{
+ struct list_head *list = page->list.prev;
+
+ return rb_list_head(list->next) != &page->list;
+}
+
+/*
+ * rb_set_list_to_head - set a list_head to be pointing to head.
+ */
+static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer,
+ struct list_head *list)
+{
+ unsigned long *ptr;
+
+ ptr = (unsigned long *)&list->next;
+ *ptr |= RB_PAGE_HEAD;
+ *ptr &= ~RB_PAGE_UPDATE;
+}
+
+/*
+ * rb_head_page_activate - sets up head page
+ */
+static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ struct buffer_page *head;
+
+ head = cpu_buffer->head_page;
+ if (!head)
+ return;
+
+ /*
+ * Set the previous list pointer to have the HEAD flag.
+ */
+ rb_set_list_to_head(cpu_buffer, head->list.prev);
+}
+
+static void rb_list_head_clear(struct list_head *list)
+{
+ unsigned long *ptr = (unsigned long *)&list->next;
+
+ *ptr &= ~RB_FLAG_MASK;
+}
+
+/*
+ * rb_head_page_dactivate - clears head page ptr (for free list)
+ */
+static void
+rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ struct list_head *hd;
+
+ /* Go through the whole list and clear any pointers found. */
+ rb_list_head_clear(cpu_buffer->pages);
+
+ list_for_each(hd, cpu_buffer->pages)
+ rb_list_head_clear(hd);
+}
+
+static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
+ struct buffer_page *head,
+ struct buffer_page *prev,
+ int old_flag, int new_flag)
+{
+ struct list_head *list;
+ unsigned long val = (unsigned long)&head->list;
+ unsigned long ret;
+
+ list = &prev->list;
+
+ val &= ~RB_FLAG_MASK;
+
+ ret = cmpxchg((unsigned long *)&list->next,
+ val | old_flag, val | new_flag);
+
+ /* check if the reader took the page */
+ if ((ret & ~RB_FLAG_MASK) != val)
+ return RB_PAGE_MOVED;
+
+ return ret & RB_FLAG_MASK;
+}
+
+static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
+ struct buffer_page *head,
+ struct buffer_page *prev,
+ int old_flag)
+{
+ return rb_head_page_set(cpu_buffer, head, prev,
+ old_flag, RB_PAGE_UPDATE);
+}
+
+static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
+ struct buffer_page *head,
+ struct buffer_page *prev,
+ int old_flag)
+{
+ return rb_head_page_set(cpu_buffer, head, prev,
+ old_flag, RB_PAGE_HEAD);
+}
+
+static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
+ struct buffer_page *head,
+ struct buffer_page *prev,
+ int old_flag)
+{
+ return rb_head_page_set(cpu_buffer, head, prev,
+ old_flag, RB_PAGE_NORMAL);
+}
+
+static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
+ struct buffer_page **bpage)
+{
+ struct list_head *p = rb_list_head((*bpage)->list.next);
+
+ *bpage = list_entry(p, struct buffer_page, list);
+}
+
+static struct buffer_page *
+rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ struct buffer_page *head;
+ struct buffer_page *page;
+ struct list_head *list;
+ int i;
+
+ if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
+ return NULL;
+
+ /* sanity check */
+ list = cpu_buffer->pages;
+ if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
+ return NULL;
+
+ page = head = cpu_buffer->head_page;
+ /*
+ * It is possible that the writer moves the header behind
+ * where we started, and we miss in one loop.
+ * A second loop should grab the header, but we'll do
+ * three loops just because I'm paranoid.
+ */
+ for (i = 0; i < 3; i++) {
+ do {
+ if (rb_is_head_page(cpu_buffer, page, page->list.prev)) {
+ cpu_buffer->head_page = page;
+ return page;
+ }
+ rb_inc_page(cpu_buffer, &page);
+ } while (page != head);
+ }
+
+ RB_WARN_ON(cpu_buffer, 1);
+
+ return NULL;
+}
+
+static int rb_head_page_replace(struct buffer_page *old,
+ struct buffer_page *new)
+{
+ unsigned long *ptr = (unsigned long *)&old->list.prev->next;
+ unsigned long val;
+ unsigned long ret;
+
+ val = *ptr & ~RB_FLAG_MASK;
+ val |= RB_PAGE_HEAD;
+
+ ret = cmpxchg(ptr, val, (unsigned long)&new->list);
+
+ return ret == val;
+}
+
+/*
+ * rb_tail_page_update - move the tail page forward
+ *
+ * Returns 1 if moved tail page, 0 if someone else did.
+ */
+static int rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
+ struct buffer_page *tail_page,
+ struct buffer_page *next_page)
+{
+ struct buffer_page *old_tail;
+ unsigned long old_entries;
+ unsigned long old_write;
+ int ret = 0;
+
+ /*
+ * The tail page now needs to be moved forward.
+ *
+ * We need to reset the tail page, but without messing
+ * with possible erasing of data brought in by interrupts
+ * that have moved the tail page and are currently on it.
+ *
+ * We add a counter to the write field to denote this.
+ */
+ old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
+ old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
+
+ /*
+ * Just make sure we have seen our old_write and synchronize
+ * with any interrupts that come in.
+ */
+ barrier();
+
+ /*
+ * If the tail page is still the same as what we think
+ * it is, then it is up to us to update the tail
+ * pointer.
+ */
+ if (tail_page == cpu_buffer->tail_page) {
+ /* Zero the write counter */
+ unsigned long val = old_write & ~RB_WRITE_MASK;
+ unsigned long eval = old_entries & ~RB_WRITE_MASK;
+
+ /*
+ * This will only succeed if an interrupt did
+ * not come in and change it. In which case, we
+ * do not want to modify it.
+ *
+ * We add (void) to let the compiler know that we do not care
+ * about the return value of these functions. We use the
+ * cmpxchg to only update if an interrupt did not already
+ * do it for us. If the cmpxchg fails, we don't care.
+ */
+ (void)local_cmpxchg(&next_page->write, old_write, val);
+ (void)local_cmpxchg(&next_page->entries, old_entries, eval);
+
+ /*
+ * No need to worry about races with clearing out the commit.
+ * it only can increment when a commit takes place. But that
+ * only happens in the outer most nested commit.
+ */
+ local_set(&next_page->page->commit, 0);
+
+ old_tail = cmpxchg(&cpu_buffer->tail_page,
+ tail_page, next_page);
+
+ if (old_tail == tail_page)
+ ret = 1;
+ }
+
+ return ret;
+}
+
+static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
+ struct buffer_page *bpage)
+{
+ unsigned long val = (unsigned long)bpage;
+
+ if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
+ return 1;
+
+ return 0;
+}
+
+/**
+ * rb_check_list - make sure a pointer to a list has the last bits zero
+ */
+static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
+ struct list_head *list)
+{
+ if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
+ return 1;
+ if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
+ return 1;
+ return 0;
+}
+
+/**
+ * rb_check_pages - integrity check of buffer pages
+ * @cpu_buffer: CPU buffer with pages to test
+ *
+ * As a safety measure we check to make sure the data pages have not
+ * been corrupted.
+ */
+static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ struct list_head *head = cpu_buffer->pages;
+ struct buffer_page *bpage, *tmp;
+
+ /* Reset the head page if it exists */
+ if (cpu_buffer->head_page)
+ rb_set_head_page(cpu_buffer);
+
+ rb_head_page_deactivate(cpu_buffer);
+
+ if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
+ return -1;
+ if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
+ return -1;
+
+ if (rb_check_list(cpu_buffer, head))
+ return -1;
+
+ list_for_each_entry_safe(bpage, tmp, head, list) {
+ if (RB_WARN_ON(cpu_buffer,
+ bpage->list.next->prev != &bpage->list))
+ return -1;
+ if (RB_WARN_ON(cpu_buffer,
+ bpage->list.prev->next != &bpage->list))
+ return -1;
+ if (rb_check_list(cpu_buffer, &bpage->list))
+ return -1;
+ }
+
+ rb_head_page_activate(cpu_buffer);
+
+ return 0;
+}
+
+static int __rb_allocate_pages(int nr_pages, struct list_head *pages, int cpu)
+{
+ int i;
+ struct buffer_page *bpage, *tmp;
+
+ for (i = 0; i < nr_pages; i++) {
+ struct page *page;
+ /*
+ * __GFP_NORETRY flag makes sure that the allocation fails
+ * gracefully without invoking oom-killer and the system is
+ * not destabilized.
+ */
+ bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
+ GFP_KERNEL | __GFP_NORETRY,
+ cpu_to_node(cpu));
+ if (!bpage)
+ goto free_pages;
+
+ list_add(&bpage->list, pages);
+
+ page = alloc_pages_node(cpu_to_node(cpu),
+ GFP_KERNEL | __GFP_NORETRY, 0);
+ if (!page)
+ goto free_pages;
+ bpage->page = page_address(page);
+ rb_init_page(bpage->page);
+ }
+
+ return 0;
+
+free_pages:
+ list_for_each_entry_safe(bpage, tmp, pages, list) {
+ list_del_init(&bpage->list);
+ free_buffer_page(bpage);
+ }
+
+ return -ENOMEM;
+}
+
+static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
+ unsigned nr_pages)
+{
+ LIST_HEAD(pages);
+
+ WARN_ON(!nr_pages);
+
+ if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu))
+ return -ENOMEM;
+
+ /*
+ * The ring buffer page list is a circular list that does not
+ * start and end with a list head. All page list items point to
+ * other pages.
+ */
+ cpu_buffer->pages = pages.next;
+ list_del(&pages);
+
+ cpu_buffer->nr_pages = nr_pages;
+
+ rb_check_pages(cpu_buffer);
+
+ return 0;
+}
+
+static struct ring_buffer_per_cpu *
+rb_allocate_cpu_buffer(struct ring_buffer *buffer, int nr_pages, int cpu)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ struct buffer_page *bpage;
+ struct page *page;
+ int ret;
+
+ cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
+ GFP_KERNEL, cpu_to_node(cpu));
+ if (!cpu_buffer)
+ return NULL;
+
+ cpu_buffer->cpu = cpu;
+ cpu_buffer->buffer = buffer;
+ raw_spin_lock_init(&cpu_buffer->reader_lock);
+ lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
+ cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
+ INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
+ init_completion(&cpu_buffer->update_done);
+ init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
+ init_waitqueue_head(&cpu_buffer->irq_work.waiters);
+ init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
+
+ bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
+ GFP_KERNEL, cpu_to_node(cpu));
+ if (!bpage)
+ goto fail_free_buffer;
+
+ rb_check_bpage(cpu_buffer, bpage);
+
+ cpu_buffer->reader_page = bpage;
+ page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0);
+ if (!page)
+ goto fail_free_reader;
+ bpage->page = page_address(page);
+ rb_init_page(bpage->page);
+
+ INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
+ INIT_LIST_HEAD(&cpu_buffer->new_pages);
+
+ ret = rb_allocate_pages(cpu_buffer, nr_pages);
+ if (ret < 0)
+ goto fail_free_reader;
+
+ cpu_buffer->head_page
+ = list_entry(cpu_buffer->pages, struct buffer_page, list);
+ cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
+
+ rb_head_page_activate(cpu_buffer);
+
+ return cpu_buffer;
+
+ fail_free_reader:
+ free_buffer_page(cpu_buffer->reader_page);
+
+ fail_free_buffer:
+ kfree(cpu_buffer);
+ return NULL;
+}
+
+static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ struct list_head *head = cpu_buffer->pages;
+ struct buffer_page *bpage, *tmp;
+
+ free_buffer_page(cpu_buffer->reader_page);
+
+ rb_head_page_deactivate(cpu_buffer);
+
+ if (head) {
+ list_for_each_entry_safe(bpage, tmp, head, list) {
+ list_del_init(&bpage->list);
+ free_buffer_page(bpage);
+ }
+ bpage = list_entry(head, struct buffer_page, list);
+ free_buffer_page(bpage);
+ }
+
+ kfree(cpu_buffer);
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+static int rb_cpu_notify(struct notifier_block *self,
+ unsigned long action, void *hcpu);
+#endif
+
+/**
+ * __ring_buffer_alloc - allocate a new ring_buffer
+ * @size: the size in bytes per cpu that is needed.
+ * @flags: attributes to set for the ring buffer.
+ *
+ * Currently the only flag that is available is the RB_FL_OVERWRITE
+ * flag. This flag means that the buffer will overwrite old data
+ * when the buffer wraps. If this flag is not set, the buffer will
+ * drop data when the tail hits the head.
+ */
+struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
+ struct lock_class_key *key)
+{
+ struct ring_buffer *buffer;
+ int bsize;
+ int cpu, nr_pages;
+
+ /* keep it in its own cache line */
+ buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
+ GFP_KERNEL);
+ if (!buffer)
+ return NULL;
+
+ if (!alloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
+ goto fail_free_buffer;
+
+ nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
+ buffer->flags = flags;
+ buffer->clock = trace_clock_local;
+ buffer->reader_lock_key = key;
+
+ init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
+ init_waitqueue_head(&buffer->irq_work.waiters);
+
+ /* need at least two pages */
+ if (nr_pages < 2)
+ nr_pages = 2;
+
+ /*
+ * In case of non-hotplug cpu, if the ring-buffer is allocated
+ * in early initcall, it will not be notified of secondary cpus.
+ * In that off case, we need to allocate for all possible cpus.
+ */
+#ifdef CONFIG_HOTPLUG_CPU
+ cpu_notifier_register_begin();
+ cpumask_copy(buffer->cpumask, cpu_online_mask);
+#else
+ cpumask_copy(buffer->cpumask, cpu_possible_mask);
+#endif
+ buffer->cpus = nr_cpu_ids;
+
+ bsize = sizeof(void *) * nr_cpu_ids;
+ buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
+ GFP_KERNEL);
+ if (!buffer->buffers)
+ goto fail_free_cpumask;
+
+ for_each_buffer_cpu(buffer, cpu) {
+ buffer->buffers[cpu] =
+ rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
+ if (!buffer->buffers[cpu])
+ goto fail_free_buffers;
+ }
+
+#ifdef CONFIG_HOTPLUG_CPU
+ buffer->cpu_notify.notifier_call = rb_cpu_notify;
+ buffer->cpu_notify.priority = 0;
+ __register_cpu_notifier(&buffer->cpu_notify);
+ cpu_notifier_register_done();
+#endif
+
+ mutex_init(&buffer->mutex);
+
+ return buffer;
+
+ fail_free_buffers:
+ for_each_buffer_cpu(buffer, cpu) {
+ if (buffer->buffers[cpu])
+ rb_free_cpu_buffer(buffer->buffers[cpu]);
+ }
+ kfree(buffer->buffers);
+
+ fail_free_cpumask:
+ free_cpumask_var(buffer->cpumask);
+#ifdef CONFIG_HOTPLUG_CPU
+ cpu_notifier_register_done();
+#endif
+
+ fail_free_buffer:
+ kfree(buffer);
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
+
+/**
+ * ring_buffer_free - free a ring buffer.
+ * @buffer: the buffer to free.
+ */
+void
+ring_buffer_free(struct ring_buffer *buffer)
+{
+ int cpu;
+
+#ifdef CONFIG_HOTPLUG_CPU
+ cpu_notifier_register_begin();
+ __unregister_cpu_notifier(&buffer->cpu_notify);
+#endif
+
+ for_each_buffer_cpu(buffer, cpu)
+ rb_free_cpu_buffer(buffer->buffers[cpu]);
+
+#ifdef CONFIG_HOTPLUG_CPU
+ cpu_notifier_register_done();
+#endif
+
+ kfree(buffer->buffers);
+ free_cpumask_var(buffer->cpumask);
+
+ kfree(buffer);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_free);
+
+void ring_buffer_set_clock(struct ring_buffer *buffer,
+ u64 (*clock)(void))
+{
+ buffer->clock = clock;
+}
+
+static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
+
+static inline unsigned long rb_page_entries(struct buffer_page *bpage)
+{
+ return local_read(&bpage->entries) & RB_WRITE_MASK;
+}
+
+static inline unsigned long rb_page_write(struct buffer_page *bpage)
+{
+ return local_read(&bpage->write) & RB_WRITE_MASK;
+}
+
+static int
+rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned int nr_pages)
+{
+ struct list_head *tail_page, *to_remove, *next_page;
+ struct buffer_page *to_remove_page, *tmp_iter_page;
+ struct buffer_page *last_page, *first_page;
+ unsigned int nr_removed;
+ unsigned long head_bit;
+ int page_entries;
+
+ head_bit = 0;
+
+ raw_spin_lock_irq(&cpu_buffer->reader_lock);
+ atomic_inc(&cpu_buffer->record_disabled);
+ /*
+ * We don't race with the readers since we have acquired the reader
+ * lock. We also don't race with writers after disabling recording.
+ * This makes it easy to figure out the first and the last page to be
+ * removed from the list. We unlink all the pages in between including
+ * the first and last pages. This is done in a busy loop so that we
+ * lose the least number of traces.
+ * The pages are freed after we restart recording and unlock readers.
+ */
+ tail_page = &cpu_buffer->tail_page->list;
+
+ /*
+ * tail page might be on reader page, we remove the next page
+ * from the ring buffer
+ */
+ if (cpu_buffer->tail_page == cpu_buffer->reader_page)
+ tail_page = rb_list_head(tail_page->next);
+ to_remove = tail_page;
+
+ /* start of pages to remove */
+ first_page = list_entry(rb_list_head(to_remove->next),
+ struct buffer_page, list);
+
+ for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
+ to_remove = rb_list_head(to_remove)->next;
+ head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
+ }
+
+ next_page = rb_list_head(to_remove)->next;
+
+ /*
+ * Now we remove all pages between tail_page and next_page.
+ * Make sure that we have head_bit value preserved for the
+ * next page
+ */
+ tail_page->next = (struct list_head *)((unsigned long)next_page |
+ head_bit);
+ next_page = rb_list_head(next_page);
+ next_page->prev = tail_page;
+
+ /* make sure pages points to a valid page in the ring buffer */
+ cpu_buffer->pages = next_page;
+
+ /* update head page */
+ if (head_bit)
+ cpu_buffer->head_page = list_entry(next_page,
+ struct buffer_page, list);
+
+ /*
+ * change read pointer to make sure any read iterators reset
+ * themselves
+ */
+ cpu_buffer->read = 0;
+
+ /* pages are removed, resume tracing and then free the pages */
+ atomic_dec(&cpu_buffer->record_disabled);
+ raw_spin_unlock_irq(&cpu_buffer->reader_lock);
+
+ RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
+
+ /* last buffer page to remove */
+ last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
+ list);
+ tmp_iter_page = first_page;
+
+ do {
+ to_remove_page = tmp_iter_page;
+ rb_inc_page(cpu_buffer, &tmp_iter_page);
+
+ /* update the counters */
+ page_entries = rb_page_entries(to_remove_page);
+ if (page_entries) {
+ /*
+ * If something was added to this page, it was full
+ * since it is not the tail page. So we deduct the
+ * bytes consumed in ring buffer from here.
+ * Increment overrun to account for the lost events.
+ */
+ local_add(page_entries, &cpu_buffer->overrun);
+ local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
+ }
+
+ /*
+ * We have already removed references to this list item, just
+ * free up the buffer_page and its page
+ */
+ free_buffer_page(to_remove_page);
+ nr_removed--;
+
+ } while (to_remove_page != last_page);
+
+ RB_WARN_ON(cpu_buffer, nr_removed);
+
+ return nr_removed == 0;
+}
+
+static int
+rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ struct list_head *pages = &cpu_buffer->new_pages;
+ int retries, success;
+
+ raw_spin_lock_irq(&cpu_buffer->reader_lock);
+ /*
+ * We are holding the reader lock, so the reader page won't be swapped
+ * in the ring buffer. Now we are racing with the writer trying to
+ * move head page and the tail page.
+ * We are going to adapt the reader page update process where:
+ * 1. We first splice the start and end of list of new pages between
+ * the head page and its previous page.
+ * 2. We cmpxchg the prev_page->next to point from head page to the
+ * start of new pages list.
+ * 3. Finally, we update the head->prev to the end of new list.
+ *
+ * We will try this process 10 times, to make sure that we don't keep
+ * spinning.
+ */
+ retries = 10;
+ success = 0;
+ while (retries--) {
+ struct list_head *head_page, *prev_page, *r;
+ struct list_head *last_page, *first_page;
+ struct list_head *head_page_with_bit;
+
+ head_page = &rb_set_head_page(cpu_buffer)->list;
+ if (!head_page)
+ break;
+ prev_page = head_page->prev;
+
+ first_page = pages->next;
+ last_page = pages->prev;
+
+ head_page_with_bit = (struct list_head *)
+ ((unsigned long)head_page | RB_PAGE_HEAD);
+
+ last_page->next = head_page_with_bit;
+ first_page->prev = prev_page;
+
+ r = cmpxchg(&prev_page->next, head_page_with_bit, first_page);
+
+ if (r == head_page_with_bit) {
+ /*
+ * yay, we replaced the page pointer to our new list,
+ * now, we just have to update to head page's prev
+ * pointer to point to end of list
+ */
+ head_page->prev = last_page;
+ success = 1;
+ break;
+ }
+ }
+
+ if (success)
+ INIT_LIST_HEAD(pages);
+ /*
+ * If we weren't successful in adding in new pages, warn and stop
+ * tracing
+ */
+ RB_WARN_ON(cpu_buffer, !success);
+ raw_spin_unlock_irq(&cpu_buffer->reader_lock);
+
+ /* free pages if they weren't inserted */
+ if (!success) {
+ struct buffer_page *bpage, *tmp;
+ list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
+ list) {
+ list_del_init(&bpage->list);
+ free_buffer_page(bpage);
+ }
+ }
+ return success;
+}
+
+static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ int success;
+
+ if (cpu_buffer->nr_pages_to_update > 0)
+ success = rb_insert_pages(cpu_buffer);
+ else
+ success = rb_remove_pages(cpu_buffer,
+ -cpu_buffer->nr_pages_to_update);
+
+ if (success)
+ cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
+}
+
+static void update_pages_handler(struct work_struct *work)
+{
+ struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
+ struct ring_buffer_per_cpu, update_pages_work);
+ rb_update_pages(cpu_buffer);
+ complete(&cpu_buffer->update_done);
+}
+
+/**
+ * ring_buffer_resize - resize the ring buffer
+ * @buffer: the buffer to resize.
+ * @size: the new size.
+ * @cpu_id: the cpu buffer to resize
+ *
+ * Minimum size is 2 * BUF_PAGE_SIZE.
+ *
+ * Returns 0 on success and < 0 on failure.
+ */
+int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
+ int cpu_id)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ unsigned nr_pages;
+ int cpu, err = 0;
+
+ /*
+ * Always succeed at resizing a non-existent buffer:
+ */
+ if (!buffer)
+ return size;
+
+ /* Make sure the requested buffer exists */
+ if (cpu_id != RING_BUFFER_ALL_CPUS &&
+ !cpumask_test_cpu(cpu_id, buffer->cpumask))
+ return size;
+
+ size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
+ size *= BUF_PAGE_SIZE;
+
+ /* we need a minimum of two pages */
+ if (size < BUF_PAGE_SIZE * 2)
+ size = BUF_PAGE_SIZE * 2;
+
+ nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
+
+ /*
+ * Don't succeed if resizing is disabled, as a reader might be
+ * manipulating the ring buffer and is expecting a sane state while
+ * this is true.
+ */
+ if (atomic_read(&buffer->resize_disabled))
+ return -EBUSY;
+
+ /* prevent another thread from changing buffer sizes */
+ mutex_lock(&buffer->mutex);
+
+ if (cpu_id == RING_BUFFER_ALL_CPUS) {
+ /* calculate the pages to update */
+ for_each_buffer_cpu(buffer, cpu) {
+ cpu_buffer = buffer->buffers[cpu];
+
+ cpu_buffer->nr_pages_to_update = nr_pages -
+ cpu_buffer->nr_pages;
+ /*
+ * nothing more to do for removing pages or no update
+ */
+ if (cpu_buffer->nr_pages_to_update <= 0)
+ continue;
+ /*
+ * to add pages, make sure all new pages can be
+ * allocated without receiving ENOMEM
+ */
+ INIT_LIST_HEAD(&cpu_buffer->new_pages);
+ if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
+ &cpu_buffer->new_pages, cpu)) {
+ /* not enough memory for new pages */
+ err = -ENOMEM;
+ goto out_err;
+ }
+ }
+
+ get_online_cpus();
+ /*
+ * Fire off all the required work handlers
+ * We can't schedule on offline CPUs, but it's not necessary
+ * since we can change their buffer sizes without any race.
+ */
+ for_each_buffer_cpu(buffer, cpu) {
+ cpu_buffer = buffer->buffers[cpu];
+ if (!cpu_buffer->nr_pages_to_update)
+ continue;
+
+ /* Can't run something on an offline CPU. */
+ if (!cpu_online(cpu)) {
+ rb_update_pages(cpu_buffer);
+ cpu_buffer->nr_pages_to_update = 0;
+ } else {
+ schedule_work_on(cpu,
+ &cpu_buffer->update_pages_work);
+ }
+ }
+
+ /* wait for all the updates to complete */
+ for_each_buffer_cpu(buffer, cpu) {
+ cpu_buffer = buffer->buffers[cpu];
+ if (!cpu_buffer->nr_pages_to_update)
+ continue;
+
+ if (cpu_online(cpu))
+ wait_for_completion(&cpu_buffer->update_done);
+ cpu_buffer->nr_pages_to_update = 0;
+ }
+
+ put_online_cpus();
+ } else {
+ /* Make sure this CPU has been intitialized */
+ if (!cpumask_test_cpu(cpu_id, buffer->cpumask))
+ goto out;
+
+ cpu_buffer = buffer->buffers[cpu_id];
+
+ if (nr_pages == cpu_buffer->nr_pages)
+ goto out;
+
+ cpu_buffer->nr_pages_to_update = nr_pages -
+ cpu_buffer->nr_pages;
+
+ INIT_LIST_HEAD(&cpu_buffer->new_pages);
+ if (cpu_buffer->nr_pages_to_update > 0 &&
+ __rb_allocate_pages(cpu_buffer->nr_pages_to_update,
+ &cpu_buffer->new_pages, cpu_id)) {
+ err = -ENOMEM;
+ goto out_err;
+ }
+
+ get_online_cpus();
+
+ /* Can't run something on an offline CPU. */
+ if (!cpu_online(cpu_id))
+ rb_update_pages(cpu_buffer);
+ else {
+ schedule_work_on(cpu_id,
+ &cpu_buffer->update_pages_work);
+ wait_for_completion(&cpu_buffer->update_done);
+ }
+
+ cpu_buffer->nr_pages_to_update = 0;
+ put_online_cpus();
+ }
+
+ out:
+ /*
+ * The ring buffer resize can happen with the ring buffer
+ * enabled, so that the update disturbs the tracing as little
+ * as possible. But if the buffer is disabled, we do not need
+ * to worry about that, and we can take the time to verify
+ * that the buffer is not corrupt.
+ */
+ if (atomic_read(&buffer->record_disabled)) {
+ atomic_inc(&buffer->record_disabled);
+ /*
+ * Even though the buffer was disabled, we must make sure
+ * that it is truly disabled before calling rb_check_pages.
+ * There could have been a race between checking
+ * record_disable and incrementing it.
+ */
+ synchronize_sched();
+ for_each_buffer_cpu(buffer, cpu) {
+ cpu_buffer = buffer->buffers[cpu];
+ rb_check_pages(cpu_buffer);
+ }
+ atomic_dec(&buffer->record_disabled);
+ }
+
+ mutex_unlock(&buffer->mutex);
+ return size;
+
+ out_err:
+ for_each_buffer_cpu(buffer, cpu) {
+ struct buffer_page *bpage, *tmp;
+
+ cpu_buffer = buffer->buffers[cpu];
+ cpu_buffer->nr_pages_to_update = 0;
+
+ if (list_empty(&cpu_buffer->new_pages))
+ continue;
+
+ list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
+ list) {
+ list_del_init(&bpage->list);
+ free_buffer_page(bpage);
+ }
+ }
+ mutex_unlock(&buffer->mutex);
+ return err;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_resize);
+
+void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val)
+{
+ mutex_lock(&buffer->mutex);
+ if (val)
+ buffer->flags |= RB_FL_OVERWRITE;
+ else
+ buffer->flags &= ~RB_FL_OVERWRITE;
+ mutex_unlock(&buffer->mutex);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
+
+static inline void *
+__rb_data_page_index(struct buffer_data_page *bpage, unsigned index)
+{
+ return bpage->data + index;
+}
+
+static inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
+{
+ return bpage->page->data + index;
+}
+
+static inline struct ring_buffer_event *
+rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ return __rb_page_index(cpu_buffer->reader_page,
+ cpu_buffer->reader_page->read);
+}
+
+static inline struct ring_buffer_event *
+rb_iter_head_event(struct ring_buffer_iter *iter)
+{
+ return __rb_page_index(iter->head_page, iter->head);
+}
+
+static inline unsigned rb_page_commit(struct buffer_page *bpage)
+{
+ return local_read(&bpage->page->commit);
+}
+
+/* Size is determined by what has been committed */
+static inline unsigned rb_page_size(struct buffer_page *bpage)
+{
+ return rb_page_commit(bpage);
+}
+
+static inline unsigned
+rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ return rb_page_commit(cpu_buffer->commit_page);
+}
+
+static inline unsigned
+rb_event_index(struct ring_buffer_event *event)
+{
+ unsigned long addr = (unsigned long)event;
+
+ return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
+}
+
+static inline int
+rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
+ struct ring_buffer_event *event)
+{
+ unsigned long addr = (unsigned long)event;
+ unsigned long index;
+
+ index = rb_event_index(event);
+ addr &= PAGE_MASK;
+
+ return cpu_buffer->commit_page->page == (void *)addr &&
+ rb_commit_index(cpu_buffer) == index;
+}
+
+static void
+rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ unsigned long max_count;
+
+ /*
+ * We only race with interrupts and NMIs on this CPU.
+ * If we own the commit event, then we can commit
+ * all others that interrupted us, since the interruptions
+ * are in stack format (they finish before they come
+ * back to us). This allows us to do a simple loop to
+ * assign the commit to the tail.
+ */
+ again:
+ max_count = cpu_buffer->nr_pages * 100;
+
+ while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
+ if (RB_WARN_ON(cpu_buffer, !(--max_count)))
+ return;
+ if (RB_WARN_ON(cpu_buffer,
+ rb_is_reader_page(cpu_buffer->tail_page)))
+ return;
+ local_set(&cpu_buffer->commit_page->page->commit,
+ rb_page_write(cpu_buffer->commit_page));
+ rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
+ cpu_buffer->write_stamp =
+ cpu_buffer->commit_page->page->time_stamp;
+ /* add barrier to keep gcc from optimizing too much */
+ barrier();
+ }
+ while (rb_commit_index(cpu_buffer) !=
+ rb_page_write(cpu_buffer->commit_page)) {
+
+ local_set(&cpu_buffer->commit_page->page->commit,
+ rb_page_write(cpu_buffer->commit_page));
+ RB_WARN_ON(cpu_buffer,
+ local_read(&cpu_buffer->commit_page->page->commit) &
+ ~RB_WRITE_MASK);
+ barrier();
+ }
+
+ /* again, keep gcc from optimizing */
+ barrier();
+
+ /*
+ * If an interrupt came in just after the first while loop
+ * and pushed the tail page forward, we will be left with
+ * a dangling commit that will never go forward.
+ */
+ if (unlikely(cpu_buffer->commit_page != cpu_buffer->tail_page))
+ goto again;
+}
+
+static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp;
+ cpu_buffer->reader_page->read = 0;
+}
+
+static void rb_inc_iter(struct ring_buffer_iter *iter)
+{
+ struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
+
+ /*
+ * The iterator could be on the reader page (it starts there).
+ * But the head could have moved, since the reader was
+ * found. Check for this case and assign the iterator
+ * to the head page instead of next.
+ */
+ if (iter->head_page == cpu_buffer->reader_page)
+ iter->head_page = rb_set_head_page(cpu_buffer);
+ else
+ rb_inc_page(cpu_buffer, &iter->head_page);
+
+ iter->read_stamp = iter->head_page->page->time_stamp;
+ iter->head = 0;
+}
+
+/* Slow path, do not inline */
+static noinline struct ring_buffer_event *
+rb_add_time_stamp(struct ring_buffer_event *event, u64 delta)
+{
+ event->type_len = RINGBUF_TYPE_TIME_EXTEND;
+
+ /* Not the first event on the page? */
+ if (rb_event_index(event)) {
+ event->time_delta = delta & TS_MASK;
+ event->array[0] = delta >> TS_SHIFT;
+ } else {
+ /* nope, just zero it */
+ event->time_delta = 0;
+ event->array[0] = 0;
+ }
+
+ return skip_time_extend(event);
+}
+
+/**
+ * rb_update_event - update event type and data
+ * @event: the event to update
+ * @type: the type of event
+ * @length: the size of the event field in the ring buffer
+ *
+ * Update the type and data fields of the event. The length
+ * is the actual size that is written to the ring buffer,
+ * and with this, we can determine what to place into the
+ * data field.
+ */
+static void
+rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
+ struct ring_buffer_event *event, unsigned length,
+ int add_timestamp, u64 delta)
+{
+ /* Only a commit updates the timestamp */
+ if (unlikely(!rb_event_is_commit(cpu_buffer, event)))
+ delta = 0;
+
+ /*
+ * If we need to add a timestamp, then we
+ * add it to the start of the resevered space.
+ */
+ if (unlikely(add_timestamp)) {
+ event = rb_add_time_stamp(event, delta);
+ length -= RB_LEN_TIME_EXTEND;
+ delta = 0;
+ }
+
+ event->time_delta = delta;
+ length -= RB_EVNT_HDR_SIZE;
+ if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
+ event->type_len = 0;
+ event->array[0] = length;
+ } else
+ event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
+}
+
+/*
+ * rb_handle_head_page - writer hit the head page
+ *
+ * Returns: +1 to retry page
+ * 0 to continue
+ * -1 on error
+ */
+static int
+rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
+ struct buffer_page *tail_page,
+ struct buffer_page *next_page)
+{
+ struct buffer_page *new_head;
+ int entries;
+ int type;
+ int ret;
+
+ entries = rb_page_entries(next_page);
+
+ /*
+ * The hard part is here. We need to move the head
+ * forward, and protect against both readers on
+ * other CPUs and writers coming in via interrupts.
+ */
+ type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
+ RB_PAGE_HEAD);
+
+ /*
+ * type can be one of four:
+ * NORMAL - an interrupt already moved it for us
+ * HEAD - we are the first to get here.
+ * UPDATE - we are the interrupt interrupting
+ * a current move.
+ * MOVED - a reader on another CPU moved the next
+ * pointer to its reader page. Give up
+ * and try again.
+ */
+
+ switch (type) {
+ case RB_PAGE_HEAD:
+ /*
+ * We changed the head to UPDATE, thus
+ * it is our responsibility to update
+ * the counters.
+ */
+ local_add(entries, &cpu_buffer->overrun);
+ local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
+
+ /*
+ * The entries will be zeroed out when we move the
+ * tail page.
+ */
+
+ /* still more to do */
+ break;
+
+ case RB_PAGE_UPDATE:
+ /*
+ * This is an interrupt that interrupt the
+ * previous update. Still more to do.
+ */
+ break;
+ case RB_PAGE_NORMAL:
+ /*
+ * An interrupt came in before the update
+ * and processed this for us.
+ * Nothing left to do.
+ */
+ return 1;
+ case RB_PAGE_MOVED:
+ /*
+ * The reader is on another CPU and just did
+ * a swap with our next_page.
+ * Try again.
+ */
+ return 1;
+ default:
+ RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
+ return -1;
+ }
+
+ /*
+ * Now that we are here, the old head pointer is
+ * set to UPDATE. This will keep the reader from
+ * swapping the head page with the reader page.
+ * The reader (on another CPU) will spin till
+ * we are finished.
+ *
+ * We just need to protect against interrupts
+ * doing the job. We will set the next pointer
+ * to HEAD. After that, we set the old pointer
+ * to NORMAL, but only if it was HEAD before.
+ * otherwise we are an interrupt, and only
+ * want the outer most commit to reset it.
+ */
+ new_head = next_page;
+ rb_inc_page(cpu_buffer, &new_head);
+
+ ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
+ RB_PAGE_NORMAL);
+
+ /*
+ * Valid returns are:
+ * HEAD - an interrupt came in and already set it.
+ * NORMAL - One of two things:
+ * 1) We really set it.
+ * 2) A bunch of interrupts came in and moved
+ * the page forward again.
+ */
+ switch (ret) {
+ case RB_PAGE_HEAD:
+ case RB_PAGE_NORMAL:
+ /* OK */
+ break;
+ default:
+ RB_WARN_ON(cpu_buffer, 1);
+ return -1;
+ }
+
+ /*
+ * It is possible that an interrupt came in,
+ * set the head up, then more interrupts came in
+ * and moved it again. When we get back here,
+ * the page would have been set to NORMAL but we
+ * just set it back to HEAD.
+ *
+ * How do you detect this? Well, if that happened
+ * the tail page would have moved.
+ */
+ if (ret == RB_PAGE_NORMAL) {
+ /*
+ * If the tail had moved passed next, then we need
+ * to reset the pointer.
+ */
+ if (cpu_buffer->tail_page != tail_page &&
+ cpu_buffer->tail_page != next_page)
+ rb_head_page_set_normal(cpu_buffer, new_head,
+ next_page,
+ RB_PAGE_HEAD);
+ }
+
+ /*
+ * If this was the outer most commit (the one that
+ * changed the original pointer from HEAD to UPDATE),
+ * then it is up to us to reset it to NORMAL.
+ */
+ if (type == RB_PAGE_HEAD) {
+ ret = rb_head_page_set_normal(cpu_buffer, next_page,
+ tail_page,
+ RB_PAGE_UPDATE);
+ if (RB_WARN_ON(cpu_buffer,
+ ret != RB_PAGE_UPDATE))
+ return -1;
+ }
+
+ return 0;
+}
+
+static unsigned rb_calculate_event_length(unsigned length)
+{
+ struct ring_buffer_event event; /* Used only for sizeof array */
+
+ /* zero length can cause confusions */
+ if (!length)
+ length = 1;
+
+ if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
+ length += sizeof(event.array[0]);
+
+ length += RB_EVNT_HDR_SIZE;
+ length = ALIGN(length, RB_ARCH_ALIGNMENT);
+
+ return length;
+}
+
+static inline void
+rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
+ struct buffer_page *tail_page,
+ unsigned long tail, unsigned long length)
+{
+ struct ring_buffer_event *event;
+
+ /*
+ * Only the event that crossed the page boundary
+ * must fill the old tail_page with padding.
+ */
+ if (tail >= BUF_PAGE_SIZE) {
+ /*
+ * If the page was filled, then we still need
+ * to update the real_end. Reset it to zero
+ * and the reader will ignore it.
+ */
+ if (tail == BUF_PAGE_SIZE)
+ tail_page->real_end = 0;
+
+ local_sub(length, &tail_page->write);
+ return;
+ }
+
+ event = __rb_page_index(tail_page, tail);
+ kmemcheck_annotate_bitfield(event, bitfield);
+
+ /* account for padding bytes */
+ local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes);
+
+ /*
+ * Save the original length to the meta data.
+ * This will be used by the reader to add lost event
+ * counter.
+ */
+ tail_page->real_end = tail;
+
+ /*
+ * If this event is bigger than the minimum size, then
+ * we need to be careful that we don't subtract the
+ * write counter enough to allow another writer to slip
+ * in on this page.
+ * We put in a discarded commit instead, to make sure
+ * that this space is not used again.
+ *
+ * If we are less than the minimum size, we don't need to
+ * worry about it.
+ */
+ if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
+ /* No room for any events */
+
+ /* Mark the rest of the page with padding */
+ rb_event_set_padding(event);
+
+ /* Set the write back to the previous setting */
+ local_sub(length, &tail_page->write);
+ return;
+ }
+
+ /* Put in a discarded event */
+ event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
+ event->type_len = RINGBUF_TYPE_PADDING;
+ /* time delta must be non zero */
+ event->time_delta = 1;
+
+ /* Set write to end of buffer */
+ length = (tail + length) - BUF_PAGE_SIZE;
+ local_sub(length, &tail_page->write);
+}
+
+/*
+ * This is the slow path, force gcc not to inline it.
+ */
+static noinline struct ring_buffer_event *
+rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
+ unsigned long length, unsigned long tail,
+ struct buffer_page *tail_page, u64 ts)
+{
+ struct buffer_page *commit_page = cpu_buffer->commit_page;
+ struct ring_buffer *buffer = cpu_buffer->buffer;
+ struct buffer_page *next_page;
+ int ret;
+
+ next_page = tail_page;
+
+ rb_inc_page(cpu_buffer, &next_page);
+
+ /*
+ * If for some reason, we had an interrupt storm that made
+ * it all the way around the buffer, bail, and warn
+ * about it.
+ */
+ if (unlikely(next_page == commit_page)) {
+ local_inc(&cpu_buffer->commit_overrun);
+ goto out_reset;
+ }
+
+ /*
+ * This is where the fun begins!
+ *
+ * We are fighting against races between a reader that
+ * could be on another CPU trying to swap its reader
+ * page with the buffer head.
+ *
+ * We are also fighting against interrupts coming in and
+ * moving the head or tail on us as well.
+ *
+ * If the next page is the head page then we have filled
+ * the buffer, unless the commit page is still on the
+ * reader page.
+ */
+ if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) {
+
+ /*
+ * If the commit is not on the reader page, then
+ * move the header page.
+ */
+ if (!rb_is_reader_page(cpu_buffer->commit_page)) {
+ /*
+ * If we are not in overwrite mode,
+ * this is easy, just stop here.
+ */
+ if (!(buffer->flags & RB_FL_OVERWRITE)) {
+ local_inc(&cpu_buffer->dropped_events);
+ goto out_reset;
+ }
+
+ ret = rb_handle_head_page(cpu_buffer,
+ tail_page,
+ next_page);
+ if (ret < 0)
+ goto out_reset;
+ if (ret)
+ goto out_again;
+ } else {
+ /*
+ * We need to be careful here too. The
+ * commit page could still be on the reader
+ * page. We could have a small buffer, and
+ * have filled up the buffer with events
+ * from interrupts and such, and wrapped.
+ *
+ * Note, if the tail page is also the on the
+ * reader_page, we let it move out.
+ */
+ if (unlikely((cpu_buffer->commit_page !=
+ cpu_buffer->tail_page) &&
+ (cpu_buffer->commit_page ==
+ cpu_buffer->reader_page))) {
+ local_inc(&cpu_buffer->commit_overrun);
+ goto out_reset;
+ }
+ }
+ }
+
+ ret = rb_tail_page_update(cpu_buffer, tail_page, next_page);
+ if (ret) {
+ /*
+ * Nested commits always have zero deltas, so
+ * just reread the time stamp
+ */
+ ts = rb_time_stamp(buffer);
+ next_page->page->time_stamp = ts;
+ }
+
+ out_again:
+
+ rb_reset_tail(cpu_buffer, tail_page, tail, length);
+
+ /* fail and let the caller try again */
+ return ERR_PTR(-EAGAIN);
+
+ out_reset:
+ /* reset write */
+ rb_reset_tail(cpu_buffer, tail_page, tail, length);
+
+ return NULL;
+}
+
+static struct ring_buffer_event *
+__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
+ unsigned long length, u64 ts,
+ u64 delta, int add_timestamp)
+{
+ struct buffer_page *tail_page;
+ struct ring_buffer_event *event;
+ unsigned long tail, write;
+
+ /*
+ * If the time delta since the last event is too big to
+ * hold in the time field of the event, then we append a
+ * TIME EXTEND event ahead of the data event.
+ */
+ if (unlikely(add_timestamp))
+ length += RB_LEN_TIME_EXTEND;
+
+ tail_page = cpu_buffer->tail_page;
+ write = local_add_return(length, &tail_page->write);
+
+ /* set write to only the index of the write */
+ write &= RB_WRITE_MASK;
+ tail = write - length;
+
+ /*
+ * If this is the first commit on the page, then it has the same
+ * timestamp as the page itself.
+ */
+ if (!tail)
+ delta = 0;
+
+ /* See if we shot pass the end of this buffer page */
+ if (unlikely(write > BUF_PAGE_SIZE))
+ return rb_move_tail(cpu_buffer, length, tail,
+ tail_page, ts);
+
+ /* We reserved something on the buffer */
+
+ event = __rb_page_index(tail_page, tail);
+ kmemcheck_annotate_bitfield(event, bitfield);
+ rb_update_event(cpu_buffer, event, length, add_timestamp, delta);
+
+ local_inc(&tail_page->entries);
+
+ /*
+ * If this is the first commit on the page, then update
+ * its timestamp.
+ */
+ if (!tail)
+ tail_page->page->time_stamp = ts;
+
+ /* account for these added bytes */
+ local_add(length, &cpu_buffer->entries_bytes);
+
+ return event;
+}
+
+static inline int
+rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
+ struct ring_buffer_event *event)
+{
+ unsigned long new_index, old_index;
+ struct buffer_page *bpage;
+ unsigned long index;
+ unsigned long addr;
+
+ new_index = rb_event_index(event);
+ old_index = new_index + rb_event_ts_length(event);
+ addr = (unsigned long)event;
+ addr &= PAGE_MASK;
+
+ bpage = cpu_buffer->tail_page;
+
+ if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
+ unsigned long write_mask =
+ local_read(&bpage->write) & ~RB_WRITE_MASK;
+ unsigned long event_length = rb_event_length(event);
+ /*
+ * This is on the tail page. It is possible that
+ * a write could come in and move the tail page
+ * and write to the next page. That is fine
+ * because we just shorten what is on this page.
+ */
+ old_index += write_mask;
+ new_index += write_mask;
+ index = local_cmpxchg(&bpage->write, old_index, new_index);
+ if (index == old_index) {
+ /* update counters */
+ local_sub(event_length, &cpu_buffer->entries_bytes);
+ return 1;
+ }
+ }
+
+ /* could not discard */
+ return 0;
+}
+
+static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ local_inc(&cpu_buffer->committing);
+ local_inc(&cpu_buffer->commits);
+}
+
+static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ unsigned long commits;
+
+ if (RB_WARN_ON(cpu_buffer,
+ !local_read(&cpu_buffer->committing)))
+ return;
+
+ again:
+ commits = local_read(&cpu_buffer->commits);
+ /* synchronize with interrupts */
+ barrier();
+ if (local_read(&cpu_buffer->committing) == 1)
+ rb_set_commit_to_write(cpu_buffer);
+
+ local_dec(&cpu_buffer->committing);
+
+ /* synchronize with interrupts */
+ barrier();
+
+ /*
+ * Need to account for interrupts coming in between the
+ * updating of the commit page and the clearing of the
+ * committing counter.
+ */
+ if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
+ !local_read(&cpu_buffer->committing)) {
+ local_inc(&cpu_buffer->committing);
+ goto again;
+ }
+}
+
+static struct ring_buffer_event *
+rb_reserve_next_event(struct ring_buffer *buffer,
+ struct ring_buffer_per_cpu *cpu_buffer,
+ unsigned long length)
+{
+ struct ring_buffer_event *event;
+ u64 ts, delta;
+ int nr_loops = 0;
+ int add_timestamp;
+ u64 diff;
+
+ rb_start_commit(cpu_buffer);
+
+#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
+ /*
+ * Due to the ability to swap a cpu buffer from a buffer
+ * it is possible it was swapped before we committed.
+ * (committing stops a swap). We check for it here and
+ * if it happened, we have to fail the write.
+ */
+ barrier();
+ if (unlikely(ACCESS_ONCE(cpu_buffer->buffer) != buffer)) {
+ local_dec(&cpu_buffer->committing);
+ local_dec(&cpu_buffer->commits);
+ return NULL;
+ }
+#endif
+
+ length = rb_calculate_event_length(length);
+ again:
+ add_timestamp = 0;
+ delta = 0;
+
+ /*
+ * We allow for interrupts to reenter here and do a trace.
+ * If one does, it will cause this original code to loop
+ * back here. Even with heavy interrupts happening, this
+ * should only happen a few times in a row. If this happens
+ * 1000 times in a row, there must be either an interrupt
+ * storm or we have something buggy.
+ * Bail!
+ */
+ if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
+ goto out_fail;
+
+ ts = rb_time_stamp(cpu_buffer->buffer);
+ diff = ts - cpu_buffer->write_stamp;
+
+ /* make sure this diff is calculated here */
+ barrier();
+
+ /* Did the write stamp get updated already? */
+ if (likely(ts >= cpu_buffer->write_stamp)) {
+ delta = diff;
+ if (unlikely(test_time_stamp(delta))) {
+ int local_clock_stable = 1;
+#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
+ local_clock_stable = sched_clock_stable();
+#endif
+ WARN_ONCE(delta > (1ULL << 59),
+ KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s",
+ (unsigned long long)delta,
+ (unsigned long long)ts,
+ (unsigned long long)cpu_buffer->write_stamp,
+ local_clock_stable ? "" :
+ "If you just came from a suspend/resume,\n"
+ "please switch to the trace global clock:\n"
+ " echo global > /sys/kernel/debug/tracing/trace_clock\n");
+ add_timestamp = 1;
+ }
+ }
+
+ event = __rb_reserve_next(cpu_buffer, length, ts,
+ delta, add_timestamp);
+ if (unlikely(PTR_ERR(event) == -EAGAIN))
+ goto again;
+
+ if (!event)
+ goto out_fail;
+
+ return event;
+
+ out_fail:
+ rb_end_commit(cpu_buffer);
+ return NULL;
+}
+
+#ifdef CONFIG_TRACING
+
+/*
+ * The lock and unlock are done within a preempt disable section.
+ * The current_context per_cpu variable can only be modified
+ * by the current task between lock and unlock. But it can
+ * be modified more than once via an interrupt. To pass this
+ * information from the lock to the unlock without having to
+ * access the 'in_interrupt()' functions again (which do show
+ * a bit of overhead in something as critical as function tracing,
+ * we use a bitmask trick.
+ *
+ * bit 0 = NMI context
+ * bit 1 = IRQ context
+ * bit 2 = SoftIRQ context
+ * bit 3 = normal context.
+ *
+ * This works because this is the order of contexts that can
+ * preempt other contexts. A SoftIRQ never preempts an IRQ
+ * context.
+ *
+ * When the context is determined, the corresponding bit is
+ * checked and set (if it was set, then a recursion of that context
+ * happened).
+ *
+ * On unlock, we need to clear this bit. To do so, just subtract
+ * 1 from the current_context and AND it to itself.
+ *
+ * (binary)
+ * 101 - 1 = 100
+ * 101 & 100 = 100 (clearing bit zero)
+ *
+ * 1010 - 1 = 1001
+ * 1010 & 1001 = 1000 (clearing bit 1)
+ *
+ * The least significant bit can be cleared this way, and it
+ * just so happens that it is the same bit corresponding to
+ * the current context.
+ */
+static DEFINE_PER_CPU(unsigned int, current_context);
+
+static __always_inline int trace_recursive_lock(void)
+{
+ unsigned int val = __this_cpu_read(current_context);
+ int bit;
+
+ if (in_interrupt()) {
+ if (in_nmi())
+ bit = 0;
+ else if (in_irq())
+ bit = 1;
+ else
+ bit = 2;
+ } else
+ bit = 3;
+
+ if (unlikely(val & (1 << bit)))
+ return 1;
+
+ val |= (1 << bit);
+ __this_cpu_write(current_context, val);
+
+ return 0;
+}
+
+static __always_inline void trace_recursive_unlock(void)
+{
+ __this_cpu_and(current_context, __this_cpu_read(current_context) - 1);
+}
+
+#else
+
+#define trace_recursive_lock() (0)
+#define trace_recursive_unlock() do { } while (0)
+
+#endif
+
+/**
+ * ring_buffer_lock_reserve - reserve a part of the buffer
+ * @buffer: the ring buffer to reserve from
+ * @length: the length of the data to reserve (excluding event header)
+ *
+ * Returns a reseverd event on the ring buffer to copy directly to.
+ * The user of this interface will need to get the body to write into
+ * and can use the ring_buffer_event_data() interface.
+ *
+ * The length is the length of the data needed, not the event length
+ * which also includes the event header.
+ *
+ * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
+ * If NULL is returned, then nothing has been allocated or locked.
+ */
+struct ring_buffer_event *
+ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ struct ring_buffer_event *event;
+ int cpu;
+
+ if (ring_buffer_flags != RB_BUFFERS_ON)
+ return NULL;
+
+ /* If we are tracing schedule, we don't want to recurse */
+ preempt_disable_notrace();
+
+ if (atomic_read(&buffer->record_disabled))
+ goto out_nocheck;
+
+ if (trace_recursive_lock())
+ goto out_nocheck;
+
+ cpu = raw_smp_processor_id();
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ goto out;
+
+ cpu_buffer = buffer->buffers[cpu];
+
+ if (atomic_read(&cpu_buffer->record_disabled))
+ goto out;
+
+ if (length > BUF_MAX_DATA_SIZE)
+ goto out;
+
+ event = rb_reserve_next_event(buffer, cpu_buffer, length);
+ if (!event)
+ goto out;
+
+ return event;
+
+ out:
+ trace_recursive_unlock();
+
+ out_nocheck:
+ preempt_enable_notrace();
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
+
+static void
+rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer,
+ struct ring_buffer_event *event)
+{
+ u64 delta;
+
+ /*
+ * The event first in the commit queue updates the
+ * time stamp.
+ */
+ if (rb_event_is_commit(cpu_buffer, event)) {
+ /*
+ * A commit event that is first on a page
+ * updates the write timestamp with the page stamp
+ */
+ if (!rb_event_index(event))
+ cpu_buffer->write_stamp =
+ cpu_buffer->commit_page->page->time_stamp;
+ else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
+ delta = event->array[0];
+ delta <<= TS_SHIFT;
+ delta += event->time_delta;
+ cpu_buffer->write_stamp += delta;
+ } else
+ cpu_buffer->write_stamp += event->time_delta;
+ }
+}
+
+static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
+ struct ring_buffer_event *event)
+{
+ local_inc(&cpu_buffer->entries);
+ rb_update_write_stamp(cpu_buffer, event);
+ rb_end_commit(cpu_buffer);
+}
+
+static __always_inline void
+rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
+{
+ bool pagebusy;
+
+ if (buffer->irq_work.waiters_pending) {
+ buffer->irq_work.waiters_pending = false;
+ /* irq_work_queue() supplies it's own memory barriers */
+ irq_work_queue(&buffer->irq_work.work);
+ }
+
+ if (cpu_buffer->irq_work.waiters_pending) {
+ cpu_buffer->irq_work.waiters_pending = false;
+ /* irq_work_queue() supplies it's own memory barriers */
+ irq_work_queue(&cpu_buffer->irq_work.work);
+ }
+
+ pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
+
+ if (!pagebusy && cpu_buffer->irq_work.full_waiters_pending) {
+ cpu_buffer->irq_work.wakeup_full = true;
+ cpu_buffer->irq_work.full_waiters_pending = false;
+ /* irq_work_queue() supplies it's own memory barriers */
+ irq_work_queue(&cpu_buffer->irq_work.work);
+ }
+}
+
+/**
+ * ring_buffer_unlock_commit - commit a reserved
+ * @buffer: The buffer to commit to
+ * @event: The event pointer to commit.
+ *
+ * This commits the data to the ring buffer, and releases any locks held.
+ *
+ * Must be paired with ring_buffer_lock_reserve.
+ */
+int ring_buffer_unlock_commit(struct ring_buffer *buffer,
+ struct ring_buffer_event *event)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ int cpu = raw_smp_processor_id();
+
+ cpu_buffer = buffer->buffers[cpu];
+
+ rb_commit(cpu_buffer, event);
+
+ rb_wakeups(buffer, cpu_buffer);
+
+ trace_recursive_unlock();
+
+ preempt_enable_notrace();
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
+
+static inline void rb_event_discard(struct ring_buffer_event *event)
+{
+ if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
+ event = skip_time_extend(event);
+
+ /* array[0] holds the actual length for the discarded event */
+ event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
+ event->type_len = RINGBUF_TYPE_PADDING;
+ /* time delta must be non zero */
+ if (!event->time_delta)
+ event->time_delta = 1;
+}
+
+/*
+ * Decrement the entries to the page that an event is on.
+ * The event does not even need to exist, only the pointer
+ * to the page it is on. This may only be called before the commit
+ * takes place.
+ */
+static inline void
+rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
+ struct ring_buffer_event *event)
+{
+ unsigned long addr = (unsigned long)event;
+ struct buffer_page *bpage = cpu_buffer->commit_page;
+ struct buffer_page *start;
+
+ addr &= PAGE_MASK;
+
+ /* Do the likely case first */
+ if (likely(bpage->page == (void *)addr)) {
+ local_dec(&bpage->entries);
+ return;
+ }
+
+ /*
+ * Because the commit page may be on the reader page we
+ * start with the next page and check the end loop there.
+ */
+ rb_inc_page(cpu_buffer, &bpage);
+ start = bpage;
+ do {
+ if (bpage->page == (void *)addr) {
+ local_dec(&bpage->entries);
+ return;
+ }
+ rb_inc_page(cpu_buffer, &bpage);
+ } while (bpage != start);
+
+ /* commit not part of this buffer?? */
+ RB_WARN_ON(cpu_buffer, 1);
+}
+
+/**
+ * ring_buffer_commit_discard - discard an event that has not been committed
+ * @buffer: the ring buffer
+ * @event: non committed event to discard
+ *
+ * Sometimes an event that is in the ring buffer needs to be ignored.
+ * This function lets the user discard an event in the ring buffer
+ * and then that event will not be read later.
+ *
+ * This function only works if it is called before the the item has been
+ * committed. It will try to free the event from the ring buffer
+ * if another event has not been added behind it.
+ *
+ * If another event has been added behind it, it will set the event
+ * up as discarded, and perform the commit.
+ *
+ * If this function is called, do not call ring_buffer_unlock_commit on
+ * the event.
+ */
+void ring_buffer_discard_commit(struct ring_buffer *buffer,
+ struct ring_buffer_event *event)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ int cpu;
+
+ /* The event is discarded regardless */
+ rb_event_discard(event);
+
+ cpu = smp_processor_id();
+ cpu_buffer = buffer->buffers[cpu];
+
+ /*
+ * This must only be called if the event has not been
+ * committed yet. Thus we can assume that preemption
+ * is still disabled.
+ */
+ RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
+
+ rb_decrement_entry(cpu_buffer, event);
+ if (rb_try_to_discard(cpu_buffer, event))
+ goto out;
+
+ /*
+ * The commit is still visible by the reader, so we
+ * must still update the timestamp.
+ */
+ rb_update_write_stamp(cpu_buffer, event);
+ out:
+ rb_end_commit(cpu_buffer);
+
+ trace_recursive_unlock();
+
+ preempt_enable_notrace();
+
+}
+EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
+
+/**
+ * ring_buffer_write - write data to the buffer without reserving
+ * @buffer: The ring buffer to write to.
+ * @length: The length of the data being written (excluding the event header)
+ * @data: The data to write to the buffer.
+ *
+ * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
+ * one function. If you already have the data to write to the buffer, it
+ * may be easier to simply call this function.
+ *
+ * Note, like ring_buffer_lock_reserve, the length is the length of the data
+ * and not the length of the event which would hold the header.
+ */
+int ring_buffer_write(struct ring_buffer *buffer,
+ unsigned long length,
+ void *data)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ struct ring_buffer_event *event;
+ void *body;
+ int ret = -EBUSY;
+ int cpu;
+
+ if (ring_buffer_flags != RB_BUFFERS_ON)
+ return -EBUSY;
+
+ preempt_disable_notrace();
+
+ if (atomic_read(&buffer->record_disabled))
+ goto out;
+
+ cpu = raw_smp_processor_id();
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ goto out;
+
+ cpu_buffer = buffer->buffers[cpu];
+
+ if (atomic_read(&cpu_buffer->record_disabled))
+ goto out;
+
+ if (length > BUF_MAX_DATA_SIZE)
+ goto out;
+
+ event = rb_reserve_next_event(buffer, cpu_buffer, length);
+ if (!event)
+ goto out;
+
+ body = rb_event_data(event);
+
+ memcpy(body, data, length);
+
+ rb_commit(cpu_buffer, event);
+
+ rb_wakeups(buffer, cpu_buffer);
+
+ ret = 0;
+ out:
+ preempt_enable_notrace();
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_write);
+
+static int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ struct buffer_page *reader = cpu_buffer->reader_page;
+ struct buffer_page *head = rb_set_head_page(cpu_buffer);
+ struct buffer_page *commit = cpu_buffer->commit_page;
+
+ /* In case of error, head will be NULL */
+ if (unlikely(!head))
+ return 1;
+
+ return reader->read == rb_page_commit(reader) &&
+ (commit == reader ||
+ (commit == head &&
+ head->read == rb_page_commit(commit)));
+}
+
+/**
+ * ring_buffer_record_disable - stop all writes into the buffer
+ * @buffer: The ring buffer to stop writes to.
+ *
+ * This prevents all writes to the buffer. Any attempt to write
+ * to the buffer after this will fail and return NULL.
+ *
+ * The caller should call synchronize_sched() after this.
+ */
+void ring_buffer_record_disable(struct ring_buffer *buffer)
+{
+ atomic_inc(&buffer->record_disabled);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
+
+/**
+ * ring_buffer_record_enable - enable writes to the buffer
+ * @buffer: The ring buffer to enable writes
+ *
+ * Note, multiple disables will need the same number of enables
+ * to truly enable the writing (much like preempt_disable).
+ */
+void ring_buffer_record_enable(struct ring_buffer *buffer)
+{
+ atomic_dec(&buffer->record_disabled);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
+
+/**
+ * ring_buffer_record_off - stop all writes into the buffer
+ * @buffer: The ring buffer to stop writes to.
+ *
+ * This prevents all writes to the buffer. Any attempt to write
+ * to the buffer after this will fail and return NULL.
+ *
+ * This is different than ring_buffer_record_disable() as
+ * it works like an on/off switch, where as the disable() version
+ * must be paired with a enable().
+ */
+void ring_buffer_record_off(struct ring_buffer *buffer)
+{
+ unsigned int rd;
+ unsigned int new_rd;
+
+ do {
+ rd = atomic_read(&buffer->record_disabled);
+ new_rd = rd | RB_BUFFER_OFF;
+ } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_record_off);
+
+/**
+ * ring_buffer_record_on - restart writes into the buffer
+ * @buffer: The ring buffer to start writes to.
+ *
+ * This enables all writes to the buffer that was disabled by
+ * ring_buffer_record_off().
+ *
+ * This is different than ring_buffer_record_enable() as
+ * it works like an on/off switch, where as the enable() version
+ * must be paired with a disable().
+ */
+void ring_buffer_record_on(struct ring_buffer *buffer)
+{
+ unsigned int rd;
+ unsigned int new_rd;
+
+ do {
+ rd = atomic_read(&buffer->record_disabled);
+ new_rd = rd & ~RB_BUFFER_OFF;
+ } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_record_on);
+
+/**
+ * ring_buffer_record_is_on - return true if the ring buffer can write
+ * @buffer: The ring buffer to see if write is enabled
+ *
+ * Returns true if the ring buffer is in a state that it accepts writes.
+ */
+int ring_buffer_record_is_on(struct ring_buffer *buffer)
+{
+ return !atomic_read(&buffer->record_disabled);
+}
+
+/**
+ * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
+ * @buffer: The ring buffer to stop writes to.
+ * @cpu: The CPU buffer to stop
+ *
+ * This prevents all writes to the buffer. Any attempt to write
+ * to the buffer after this will fail and return NULL.
+ *
+ * The caller should call synchronize_sched() after this.
+ */
+void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ return;
+
+ cpu_buffer = buffer->buffers[cpu];
+ atomic_inc(&cpu_buffer->record_disabled);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
+
+/**
+ * ring_buffer_record_enable_cpu - enable writes to the buffer
+ * @buffer: The ring buffer to enable writes
+ * @cpu: The CPU to enable.
+ *
+ * Note, multiple disables will need the same number of enables
+ * to truly enable the writing (much like preempt_disable).
+ */
+void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ return;
+
+ cpu_buffer = buffer->buffers[cpu];
+ atomic_dec(&cpu_buffer->record_disabled);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
+
+/*
+ * The total entries in the ring buffer is the running counter
+ * of entries entered into the ring buffer, minus the sum of
+ * the entries read from the ring buffer and the number of
+ * entries that were overwritten.
+ */
+static inline unsigned long
+rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ return local_read(&cpu_buffer->entries) -
+ (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
+}
+
+/**
+ * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
+ * @buffer: The ring buffer
+ * @cpu: The per CPU buffer to read from.
+ */
+u64 ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu)
+{
+ unsigned long flags;
+ struct ring_buffer_per_cpu *cpu_buffer;
+ struct buffer_page *bpage;
+ u64 ret = 0;
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ return 0;
+
+ cpu_buffer = buffer->buffers[cpu];
+ raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+ /*
+ * if the tail is on reader_page, oldest time stamp is on the reader
+ * page
+ */
+ if (cpu_buffer->tail_page == cpu_buffer->reader_page)
+ bpage = cpu_buffer->reader_page;
+ else
+ bpage = rb_set_head_page(cpu_buffer);
+ if (bpage)
+ ret = bpage->page->time_stamp;
+ raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
+
+/**
+ * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
+ * @buffer: The ring buffer
+ * @cpu: The per CPU buffer to read from.
+ */
+unsigned long ring_buffer_bytes_cpu(struct ring_buffer *buffer, int cpu)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ unsigned long ret;
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ return 0;
+
+ cpu_buffer = buffer->buffers[cpu];
+ ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
+
+/**
+ * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
+ * @buffer: The ring buffer
+ * @cpu: The per CPU buffer to get the entries from.
+ */
+unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ return 0;
+
+ cpu_buffer = buffer->buffers[cpu];
+
+ return rb_num_of_entries(cpu_buffer);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
+
+/**
+ * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
+ * buffer wrapping around (only if RB_FL_OVERWRITE is on).
+ * @buffer: The ring buffer
+ * @cpu: The per CPU buffer to get the number of overruns from
+ */
+unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ unsigned long ret;
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ return 0;
+
+ cpu_buffer = buffer->buffers[cpu];
+ ret = local_read(&cpu_buffer->overrun);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
+
+/**
+ * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
+ * commits failing due to the buffer wrapping around while there are uncommitted
+ * events, such as during an interrupt storm.
+ * @buffer: The ring buffer
+ * @cpu: The per CPU buffer to get the number of overruns from
+ */
+unsigned long
+ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ unsigned long ret;
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ return 0;
+
+ cpu_buffer = buffer->buffers[cpu];
+ ret = local_read(&cpu_buffer->commit_overrun);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
+
+/**
+ * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
+ * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
+ * @buffer: The ring buffer
+ * @cpu: The per CPU buffer to get the number of overruns from
+ */
+unsigned long
+ring_buffer_dropped_events_cpu(struct ring_buffer *buffer, int cpu)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ unsigned long ret;
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ return 0;
+
+ cpu_buffer = buffer->buffers[cpu];
+ ret = local_read(&cpu_buffer->dropped_events);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
+
+/**
+ * ring_buffer_read_events_cpu - get the number of events successfully read
+ * @buffer: The ring buffer
+ * @cpu: The per CPU buffer to get the number of events read
+ */
+unsigned long
+ring_buffer_read_events_cpu(struct ring_buffer *buffer, int cpu)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ return 0;
+
+ cpu_buffer = buffer->buffers[cpu];
+ return cpu_buffer->read;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
+
+/**
+ * ring_buffer_entries - get the number of entries in a buffer
+ * @buffer: The ring buffer
+ *
+ * Returns the total number of entries in the ring buffer
+ * (all CPU entries)
+ */
+unsigned long ring_buffer_entries(struct ring_buffer *buffer)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ unsigned long entries = 0;
+ int cpu;
+
+ /* if you care about this being correct, lock the buffer */
+ for_each_buffer_cpu(buffer, cpu) {
+ cpu_buffer = buffer->buffers[cpu];
+ entries += rb_num_of_entries(cpu_buffer);
+ }
+
+ return entries;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_entries);
+
+/**
+ * ring_buffer_overruns - get the number of overruns in buffer
+ * @buffer: The ring buffer
+ *
+ * Returns the total number of overruns in the ring buffer
+ * (all CPU entries)
+ */
+unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ unsigned long overruns = 0;
+ int cpu;
+
+ /* if you care about this being correct, lock the buffer */
+ for_each_buffer_cpu(buffer, cpu) {
+ cpu_buffer = buffer->buffers[cpu];
+ overruns += local_read(&cpu_buffer->overrun);
+ }
+
+ return overruns;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_overruns);
+
+static void rb_iter_reset(struct ring_buffer_iter *iter)
+{
+ struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
+
+ /* Iterator usage is expected to have record disabled */
+ iter->head_page = cpu_buffer->reader_page;
+ iter->head = cpu_buffer->reader_page->read;
+
+ iter->cache_reader_page = iter->head_page;
+ iter->cache_read = cpu_buffer->read;
+
+ if (iter->head)
+ iter->read_stamp = cpu_buffer->read_stamp;
+ else
+ iter->read_stamp = iter->head_page->page->time_stamp;
+}
+
+/**
+ * ring_buffer_iter_reset - reset an iterator
+ * @iter: The iterator to reset
+ *
+ * Resets the iterator, so that it will start from the beginning
+ * again.
+ */
+void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ unsigned long flags;
+
+ if (!iter)
+ return;
+
+ cpu_buffer = iter->cpu_buffer;
+
+ raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+ rb_iter_reset(iter);
+ raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
+
+/**
+ * ring_buffer_iter_empty - check if an iterator has no more to read
+ * @iter: The iterator to check
+ */
+int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+
+ cpu_buffer = iter->cpu_buffer;
+
+ return iter->head_page == cpu_buffer->commit_page &&
+ iter->head == rb_commit_index(cpu_buffer);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
+
+static void
+rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
+ struct ring_buffer_event *event)
+{
+ u64 delta;
+
+ switch (event->type_len) {
+ case RINGBUF_TYPE_PADDING:
+ return;
+
+ case RINGBUF_TYPE_TIME_EXTEND:
+ delta = event->array[0];
+ delta <<= TS_SHIFT;
+ delta += event->time_delta;
+ cpu_buffer->read_stamp += delta;
+ return;
+
+ case RINGBUF_TYPE_TIME_STAMP:
+ /* FIXME: not implemented */
+ return;
+
+ case RINGBUF_TYPE_DATA:
+ cpu_buffer->read_stamp += event->time_delta;
+ return;
+
+ default:
+ BUG();
+ }
+ return;
+}
+
+static void
+rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
+ struct ring_buffer_event *event)
+{
+ u64 delta;
+
+ switch (event->type_len) {
+ case RINGBUF_TYPE_PADDING:
+ return;
+
+ case RINGBUF_TYPE_TIME_EXTEND:
+ delta = event->array[0];
+ delta <<= TS_SHIFT;
+ delta += event->time_delta;
+ iter->read_stamp += delta;
+ return;
+
+ case RINGBUF_TYPE_TIME_STAMP:
+ /* FIXME: not implemented */
+ return;
+
+ case RINGBUF_TYPE_DATA:
+ iter->read_stamp += event->time_delta;
+ return;
+
+ default:
+ BUG();
+ }
+ return;
+}
+
+static struct buffer_page *
+rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ struct buffer_page *reader = NULL;
+ unsigned long overwrite;
+ unsigned long flags;
+ int nr_loops = 0;
+ int ret;
+
+ local_irq_save(flags);
+ arch_spin_lock(&cpu_buffer->lock);
+
+ again:
+ /*
+ * This should normally only loop twice. But because the
+ * start of the reader inserts an empty page, it causes
+ * a case where we will loop three times. There should be no
+ * reason to loop four times (that I know of).
+ */
+ if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
+ reader = NULL;
+ goto out;
+ }
+
+ reader = cpu_buffer->reader_page;
+
+ /* If there's more to read, return this page */
+ if (cpu_buffer->reader_page->read < rb_page_size(reader))
+ goto out;
+
+ /* Never should we have an index greater than the size */
+ if (RB_WARN_ON(cpu_buffer,
+ cpu_buffer->reader_page->read > rb_page_size(reader)))
+ goto out;
+
+ /* check if we caught up to the tail */
+ reader = NULL;
+ if (cpu_buffer->commit_page == cpu_buffer->reader_page)
+ goto out;
+
+ /* Don't bother swapping if the ring buffer is empty */
+ if (rb_num_of_entries(cpu_buffer) == 0)
+ goto out;
+
+ /*
+ * Reset the reader page to size zero.
+ */
+ local_set(&cpu_buffer->reader_page->write, 0);
+ local_set(&cpu_buffer->reader_page->entries, 0);
+ local_set(&cpu_buffer->reader_page->page->commit, 0);
+ cpu_buffer->reader_page->real_end = 0;
+
+ spin:
+ /*
+ * Splice the empty reader page into the list around the head.
+ */
+ reader = rb_set_head_page(cpu_buffer);
+ if (!reader)
+ goto out;
+ cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
+ cpu_buffer->reader_page->list.prev = reader->list.prev;
+
+ /*
+ * cpu_buffer->pages just needs to point to the buffer, it
+ * has no specific buffer page to point to. Lets move it out
+ * of our way so we don't accidentally swap it.
+ */
+ cpu_buffer->pages = reader->list.prev;
+
+ /* The reader page will be pointing to the new head */
+ rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list);
+
+ /*
+ * We want to make sure we read the overruns after we set up our
+ * pointers to the next object. The writer side does a
+ * cmpxchg to cross pages which acts as the mb on the writer
+ * side. Note, the reader will constantly fail the swap
+ * while the writer is updating the pointers, so this
+ * guarantees that the overwrite recorded here is the one we
+ * want to compare with the last_overrun.
+ */
+ smp_mb();
+ overwrite = local_read(&(cpu_buffer->overrun));
+
+ /*
+ * Here's the tricky part.
+ *
+ * We need to move the pointer past the header page.
+ * But we can only do that if a writer is not currently
+ * moving it. The page before the header page has the
+ * flag bit '1' set if it is pointing to the page we want.
+ * but if the writer is in the process of moving it
+ * than it will be '2' or already moved '0'.
+ */
+
+ ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
+
+ /*
+ * If we did not convert it, then we must try again.
+ */
+ if (!ret)
+ goto spin;
+
+ /*
+ * Yeah! We succeeded in replacing the page.
+ *
+ * Now make the new head point back to the reader page.
+ */
+ rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
+ rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
+
+ /* Finally update the reader page to the new head */
+ cpu_buffer->reader_page = reader;
+ rb_reset_reader_page(cpu_buffer);
+
+ if (overwrite != cpu_buffer->last_overrun) {
+ cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
+ cpu_buffer->last_overrun = overwrite;
+ }
+
+ goto again;
+
+ out:
+ arch_spin_unlock(&cpu_buffer->lock);
+ local_irq_restore(flags);
+
+ return reader;
+}
+
+static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ struct ring_buffer_event *event;
+ struct buffer_page *reader;
+ unsigned length;
+
+ reader = rb_get_reader_page(cpu_buffer);
+
+ /* This function should not be called when buffer is empty */
+ if (RB_WARN_ON(cpu_buffer, !reader))
+ return;
+
+ event = rb_reader_event(cpu_buffer);
+
+ if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
+ cpu_buffer->read++;
+
+ rb_update_read_stamp(cpu_buffer, event);
+
+ length = rb_event_length(event);
+ cpu_buffer->reader_page->read += length;
+}
+
+static void rb_advance_iter(struct ring_buffer_iter *iter)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ struct ring_buffer_event *event;
+ unsigned length;
+
+ cpu_buffer = iter->cpu_buffer;
+
+ /*
+ * Check if we are at the end of the buffer.
+ */
+ if (iter->head >= rb_page_size(iter->head_page)) {
+ /* discarded commits can make the page empty */
+ if (iter->head_page == cpu_buffer->commit_page)
+ return;
+ rb_inc_iter(iter);
+ return;
+ }
+
+ event = rb_iter_head_event(iter);
+
+ length = rb_event_length(event);
+
+ /*
+ * This should not be called to advance the header if we are
+ * at the tail of the buffer.
+ */
+ if (RB_WARN_ON(cpu_buffer,
+ (iter->head_page == cpu_buffer->commit_page) &&
+ (iter->head + length > rb_commit_index(cpu_buffer))))
+ return;
+
+ rb_update_iter_read_stamp(iter, event);
+
+ iter->head += length;
+
+ /* check for end of page padding */
+ if ((iter->head >= rb_page_size(iter->head_page)) &&
+ (iter->head_page != cpu_buffer->commit_page))
+ rb_inc_iter(iter);
+}
+
+static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ return cpu_buffer->lost_events;
+}
+
+static struct ring_buffer_event *
+rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
+ unsigned long *lost_events)
+{
+ struct ring_buffer_event *event;
+ struct buffer_page *reader;
+ int nr_loops = 0;
+
+ again:
+ /*
+ * We repeat when a time extend is encountered.
+ * Since the time extend is always attached to a data event,
+ * we should never loop more than once.
+ * (We never hit the following condition more than twice).
+ */
+ if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
+ return NULL;
+
+ reader = rb_get_reader_page(cpu_buffer);
+ if (!reader)
+ return NULL;
+
+ event = rb_reader_event(cpu_buffer);
+
+ switch (event->type_len) {
+ case RINGBUF_TYPE_PADDING:
+ if (rb_null_event(event))
+ RB_WARN_ON(cpu_buffer, 1);
+ /*
+ * Because the writer could be discarding every
+ * event it creates (which would probably be bad)
+ * if we were to go back to "again" then we may never
+ * catch up, and will trigger the warn on, or lock
+ * the box. Return the padding, and we will release
+ * the current locks, and try again.
+ */
+ return event;
+
+ case RINGBUF_TYPE_TIME_EXTEND:
+ /* Internal data, OK to advance */
+ rb_advance_reader(cpu_buffer);
+ goto again;
+
+ case RINGBUF_TYPE_TIME_STAMP:
+ /* FIXME: not implemented */
+ rb_advance_reader(cpu_buffer);
+ goto again;
+
+ case RINGBUF_TYPE_DATA:
+ if (ts) {
+ *ts = cpu_buffer->read_stamp + event->time_delta;
+ ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
+ cpu_buffer->cpu, ts);
+ }
+ if (lost_events)
+ *lost_events = rb_lost_events(cpu_buffer);
+ return event;
+
+ default:
+ BUG();
+ }
+
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_peek);
+
+static struct ring_buffer_event *
+rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
+{
+ struct ring_buffer *buffer;
+ struct ring_buffer_per_cpu *cpu_buffer;
+ struct ring_buffer_event *event;
+ int nr_loops = 0;
+
+ cpu_buffer = iter->cpu_buffer;
+ buffer = cpu_buffer->buffer;
+
+ /*
+ * Check if someone performed a consuming read to
+ * the buffer. A consuming read invalidates the iterator
+ * and we need to reset the iterator in this case.
+ */
+ if (unlikely(iter->cache_read != cpu_buffer->read ||
+ iter->cache_reader_page != cpu_buffer->reader_page))
+ rb_iter_reset(iter);
+
+ again:
+ if (ring_buffer_iter_empty(iter))
+ return NULL;
+
+ /*
+ * We repeat when a time extend is encountered or we hit
+ * the end of the page. Since the time extend is always attached
+ * to a data event, we should never loop more than three times.
+ * Once for going to next page, once on time extend, and
+ * finally once to get the event.
+ * (We never hit the following condition more than thrice).
+ */
+ if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3))
+ return NULL;
+
+ if (rb_per_cpu_empty(cpu_buffer))
+ return NULL;
+
+ if (iter->head >= rb_page_size(iter->head_page)) {
+ rb_inc_iter(iter);
+ goto again;
+ }
+
+ event = rb_iter_head_event(iter);
+
+ switch (event->type_len) {
+ case RINGBUF_TYPE_PADDING:
+ if (rb_null_event(event)) {
+ rb_inc_iter(iter);
+ goto again;
+ }
+ rb_advance_iter(iter);
+ return event;
+
+ case RINGBUF_TYPE_TIME_EXTEND:
+ /* Internal data, OK to advance */
+ rb_advance_iter(iter);
+ goto again;
+
+ case RINGBUF_TYPE_TIME_STAMP:
+ /* FIXME: not implemented */
+ rb_advance_iter(iter);
+ goto again;
+
+ case RINGBUF_TYPE_DATA:
+ if (ts) {
+ *ts = iter->read_stamp + event->time_delta;
+ ring_buffer_normalize_time_stamp(buffer,
+ cpu_buffer->cpu, ts);
+ }
+ return event;
+
+ default:
+ BUG();
+ }
+
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
+
+static inline int rb_ok_to_lock(void)
+{
+ /*
+ * If an NMI die dumps out the content of the ring buffer
+ * do not grab locks. We also permanently disable the ring
+ * buffer too. A one time deal is all you get from reading
+ * the ring buffer from an NMI.
+ */
+ if (likely(!in_nmi()))
+ return 1;
+
+ tracing_off_permanent();
+ return 0;
+}
+
+/**
+ * ring_buffer_peek - peek at the next event to be read
+ * @buffer: The ring buffer to read
+ * @cpu: The cpu to peak at
+ * @ts: The timestamp counter of this event.
+ * @lost_events: a variable to store if events were lost (may be NULL)
+ *
+ * This will return the event that will be read next, but does
+ * not consume the data.
+ */
+struct ring_buffer_event *
+ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts,
+ unsigned long *lost_events)
+{
+ struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
+ struct ring_buffer_event *event;
+ unsigned long flags;
+ int dolock;
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ return NULL;
+
+ dolock = rb_ok_to_lock();
+ again:
+ local_irq_save(flags);
+ if (dolock)
+ raw_spin_lock(&cpu_buffer->reader_lock);
+ event = rb_buffer_peek(cpu_buffer, ts, lost_events);
+ if (event && event->type_len == RINGBUF_TYPE_PADDING)
+ rb_advance_reader(cpu_buffer);
+ if (dolock)
+ raw_spin_unlock(&cpu_buffer->reader_lock);
+ local_irq_restore(flags);
+
+ if (event && event->type_len == RINGBUF_TYPE_PADDING)
+ goto again;
+
+ return event;
+}
+
+/**
+ * ring_buffer_iter_peek - peek at the next event to be read
+ * @iter: The ring buffer iterator
+ * @ts: The timestamp counter of this event.
+ *
+ * This will return the event that will be read next, but does
+ * not increment the iterator.
+ */
+struct ring_buffer_event *
+ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
+{
+ struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
+ struct ring_buffer_event *event;
+ unsigned long flags;
+
+ again:
+ raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+ event = rb_iter_peek(iter, ts);
+ raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+
+ if (event && event->type_len == RINGBUF_TYPE_PADDING)
+ goto again;
+
+ return event;
+}
+
+/**
+ * ring_buffer_consume - return an event and consume it
+ * @buffer: The ring buffer to get the next event from
+ * @cpu: the cpu to read the buffer from
+ * @ts: a variable to store the timestamp (may be NULL)
+ * @lost_events: a variable to store if events were lost (may be NULL)
+ *
+ * Returns the next event in the ring buffer, and that event is consumed.
+ * Meaning, that sequential reads will keep returning a different event,
+ * and eventually empty the ring buffer if the producer is slower.
+ */
+struct ring_buffer_event *
+ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts,
+ unsigned long *lost_events)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ struct ring_buffer_event *event = NULL;
+ unsigned long flags;
+ int dolock;
+
+ dolock = rb_ok_to_lock();
+
+ again:
+ /* might be called in atomic */
+ preempt_disable();
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ goto out;
+
+ cpu_buffer = buffer->buffers[cpu];
+ local_irq_save(flags);
+ if (dolock)
+ raw_spin_lock(&cpu_buffer->reader_lock);
+
+ event = rb_buffer_peek(cpu_buffer, ts, lost_events);
+ if (event) {
+ cpu_buffer->lost_events = 0;
+ rb_advance_reader(cpu_buffer);
+ }
+
+ if (dolock)
+ raw_spin_unlock(&cpu_buffer->reader_lock);
+ local_irq_restore(flags);
+
+ out:
+ preempt_enable();
+
+ if (event && event->type_len == RINGBUF_TYPE_PADDING)
+ goto again;
+
+ return event;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_consume);
+
+/**
+ * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
+ * @buffer: The ring buffer to read from
+ * @cpu: The cpu buffer to iterate over
+ *
+ * This performs the initial preparations necessary to iterate
+ * through the buffer. Memory is allocated, buffer recording
+ * is disabled, and the iterator pointer is returned to the caller.
+ *
+ * Disabling buffer recordng prevents the reading from being
+ * corrupted. This is not a consuming read, so a producer is not
+ * expected.
+ *
+ * After a sequence of ring_buffer_read_prepare calls, the user is
+ * expected to make at least one call to ring_buffer_read_prepare_sync.
+ * Afterwards, ring_buffer_read_start is invoked to get things going
+ * for real.
+ *
+ * This overall must be paired with ring_buffer_read_finish.
+ */
+struct ring_buffer_iter *
+ring_buffer_read_prepare(struct ring_buffer *buffer, int cpu)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ struct ring_buffer_iter *iter;
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ return NULL;
+
+ iter = kmalloc(sizeof(*iter), GFP_KERNEL);
+ if (!iter)
+ return NULL;
+
+ cpu_buffer = buffer->buffers[cpu];
+
+ iter->cpu_buffer = cpu_buffer;
+
+ atomic_inc(&buffer->resize_disabled);
+ atomic_inc(&cpu_buffer->record_disabled);
+
+ return iter;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
+
+/**
+ * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
+ *
+ * All previously invoked ring_buffer_read_prepare calls to prepare
+ * iterators will be synchronized. Afterwards, read_buffer_read_start
+ * calls on those iterators are allowed.
+ */
+void
+ring_buffer_read_prepare_sync(void)
+{
+ synchronize_sched();
+}
+EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
+
+/**
+ * ring_buffer_read_start - start a non consuming read of the buffer
+ * @iter: The iterator returned by ring_buffer_read_prepare
+ *
+ * This finalizes the startup of an iteration through the buffer.
+ * The iterator comes from a call to ring_buffer_read_prepare and
+ * an intervening ring_buffer_read_prepare_sync must have been
+ * performed.
+ *
+ * Must be paired with ring_buffer_read_finish.
+ */
+void
+ring_buffer_read_start(struct ring_buffer_iter *iter)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ unsigned long flags;
+
+ if (!iter)
+ return;
+
+ cpu_buffer = iter->cpu_buffer;
+
+ raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+ arch_spin_lock(&cpu_buffer->lock);
+ rb_iter_reset(iter);
+ arch_spin_unlock(&cpu_buffer->lock);
+ raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_read_start);
+
+/**
+ * ring_buffer_read_finish - finish reading the iterator of the buffer
+ * @iter: The iterator retrieved by ring_buffer_start
+ *
+ * This re-enables the recording to the buffer, and frees the
+ * iterator.
+ */
+void
+ring_buffer_read_finish(struct ring_buffer_iter *iter)
+{
+ struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
+ unsigned long flags;
+
+ /*
+ * Ring buffer is disabled from recording, here's a good place
+ * to check the integrity of the ring buffer.
+ * Must prevent readers from trying to read, as the check
+ * clears the HEAD page and readers require it.
+ */
+ raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+ rb_check_pages(cpu_buffer);
+ raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+
+ atomic_dec(&cpu_buffer->record_disabled);
+ atomic_dec(&cpu_buffer->buffer->resize_disabled);
+ kfree(iter);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
+
+/**
+ * ring_buffer_read - read the next item in the ring buffer by the iterator
+ * @iter: The ring buffer iterator
+ * @ts: The time stamp of the event read.
+ *
+ * This reads the next event in the ring buffer and increments the iterator.
+ */
+struct ring_buffer_event *
+ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
+{
+ struct ring_buffer_event *event;
+ struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+ again:
+ event = rb_iter_peek(iter, ts);
+ if (!event)
+ goto out;
+
+ if (event->type_len == RINGBUF_TYPE_PADDING)
+ goto again;
+
+ rb_advance_iter(iter);
+ out:
+ raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+
+ return event;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_read);
+
+/**
+ * ring_buffer_size - return the size of the ring buffer (in bytes)
+ * @buffer: The ring buffer.
+ */
+unsigned long ring_buffer_size(struct ring_buffer *buffer, int cpu)
+{
+ /*
+ * Earlier, this method returned
+ * BUF_PAGE_SIZE * buffer->nr_pages
+ * Since the nr_pages field is now removed, we have converted this to
+ * return the per cpu buffer value.
+ */
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ return 0;
+
+ return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_size);
+
+static void
+rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ rb_head_page_deactivate(cpu_buffer);
+
+ cpu_buffer->head_page
+ = list_entry(cpu_buffer->pages, struct buffer_page, list);
+ local_set(&cpu_buffer->head_page->write, 0);
+ local_set(&cpu_buffer->head_page->entries, 0);
+ local_set(&cpu_buffer->head_page->page->commit, 0);
+
+ cpu_buffer->head_page->read = 0;
+
+ cpu_buffer->tail_page = cpu_buffer->head_page;
+ cpu_buffer->commit_page = cpu_buffer->head_page;
+
+ INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
+ INIT_LIST_HEAD(&cpu_buffer->new_pages);
+ local_set(&cpu_buffer->reader_page->write, 0);
+ local_set(&cpu_buffer->reader_page->entries, 0);
+ local_set(&cpu_buffer->reader_page->page->commit, 0);
+ cpu_buffer->reader_page->read = 0;
+
+ local_set(&cpu_buffer->entries_bytes, 0);
+ local_set(&cpu_buffer->overrun, 0);
+ local_set(&cpu_buffer->commit_overrun, 0);
+ local_set(&cpu_buffer->dropped_events, 0);
+ local_set(&cpu_buffer->entries, 0);
+ local_set(&cpu_buffer->committing, 0);
+ local_set(&cpu_buffer->commits, 0);
+ cpu_buffer->read = 0;
+ cpu_buffer->read_bytes = 0;
+
+ cpu_buffer->write_stamp = 0;
+ cpu_buffer->read_stamp = 0;
+
+ cpu_buffer->lost_events = 0;
+ cpu_buffer->last_overrun = 0;
+
+ rb_head_page_activate(cpu_buffer);
+}
+
+/**
+ * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
+ * @buffer: The ring buffer to reset a per cpu buffer of
+ * @cpu: The CPU buffer to be reset
+ */
+void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
+{
+ struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
+ unsigned long flags;
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ return;
+
+ atomic_inc(&buffer->resize_disabled);
+ atomic_inc(&cpu_buffer->record_disabled);
+
+ /* Make sure all commits have finished */
+ synchronize_sched();
+
+ raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+
+ if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
+ goto out;
+
+ arch_spin_lock(&cpu_buffer->lock);
+
+ rb_reset_cpu(cpu_buffer);
+
+ arch_spin_unlock(&cpu_buffer->lock);
+
+ out:
+ raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+
+ atomic_dec(&cpu_buffer->record_disabled);
+ atomic_dec(&buffer->resize_disabled);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
+
+/**
+ * ring_buffer_reset - reset a ring buffer
+ * @buffer: The ring buffer to reset all cpu buffers
+ */
+void ring_buffer_reset(struct ring_buffer *buffer)
+{
+ int cpu;
+
+ for_each_buffer_cpu(buffer, cpu)
+ ring_buffer_reset_cpu(buffer, cpu);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_reset);
+
+/**
+ * rind_buffer_empty - is the ring buffer empty?
+ * @buffer: The ring buffer to test
+ */
+int ring_buffer_empty(struct ring_buffer *buffer)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ unsigned long flags;
+ int dolock;
+ int cpu;
+ int ret;
+
+ dolock = rb_ok_to_lock();
+
+ /* yes this is racy, but if you don't like the race, lock the buffer */
+ for_each_buffer_cpu(buffer, cpu) {
+ cpu_buffer = buffer->buffers[cpu];
+ local_irq_save(flags);
+ if (dolock)
+ raw_spin_lock(&cpu_buffer->reader_lock);
+ ret = rb_per_cpu_empty(cpu_buffer);
+ if (dolock)
+ raw_spin_unlock(&cpu_buffer->reader_lock);
+ local_irq_restore(flags);
+
+ if (!ret)
+ return 0;
+ }
+
+ return 1;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_empty);
+
+/**
+ * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
+ * @buffer: The ring buffer
+ * @cpu: The CPU buffer to test
+ */
+int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ unsigned long flags;
+ int dolock;
+ int ret;
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ return 1;
+
+ dolock = rb_ok_to_lock();
+
+ cpu_buffer = buffer->buffers[cpu];
+ local_irq_save(flags);
+ if (dolock)
+ raw_spin_lock(&cpu_buffer->reader_lock);
+ ret = rb_per_cpu_empty(cpu_buffer);
+ if (dolock)
+ raw_spin_unlock(&cpu_buffer->reader_lock);
+ local_irq_restore(flags);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
+
+#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
+/**
+ * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
+ * @buffer_a: One buffer to swap with
+ * @buffer_b: The other buffer to swap with
+ *
+ * This function is useful for tracers that want to take a "snapshot"
+ * of a CPU buffer and has another back up buffer lying around.
+ * it is expected that the tracer handles the cpu buffer not being
+ * used at the moment.
+ */
+int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
+ struct ring_buffer *buffer_b, int cpu)
+{
+ struct ring_buffer_per_cpu *cpu_buffer_a;
+ struct ring_buffer_per_cpu *cpu_buffer_b;
+ int ret = -EINVAL;
+
+ if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
+ !cpumask_test_cpu(cpu, buffer_b->cpumask))
+ goto out;
+
+ cpu_buffer_a = buffer_a->buffers[cpu];
+ cpu_buffer_b = buffer_b->buffers[cpu];
+
+ /* At least make sure the two buffers are somewhat the same */
+ if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
+ goto out;
+
+ ret = -EAGAIN;
+
+ if (ring_buffer_flags != RB_BUFFERS_ON)
+ goto out;
+
+ if (atomic_read(&buffer_a->record_disabled))
+ goto out;
+
+ if (atomic_read(&buffer_b->record_disabled))
+ goto out;
+
+ if (atomic_read(&cpu_buffer_a->record_disabled))
+ goto out;
+
+ if (atomic_read(&cpu_buffer_b->record_disabled))
+ goto out;
+
+ /*
+ * We can't do a synchronize_sched here because this
+ * function can be called in atomic context.
+ * Normally this will be called from the same CPU as cpu.
+ * If not it's up to the caller to protect this.
+ */
+ atomic_inc(&cpu_buffer_a->record_disabled);
+ atomic_inc(&cpu_buffer_b->record_disabled);
+
+ ret = -EBUSY;
+ if (local_read(&cpu_buffer_a->committing))
+ goto out_dec;
+ if (local_read(&cpu_buffer_b->committing))
+ goto out_dec;
+
+ buffer_a->buffers[cpu] = cpu_buffer_b;
+ buffer_b->buffers[cpu] = cpu_buffer_a;
+
+ cpu_buffer_b->buffer = buffer_a;
+ cpu_buffer_a->buffer = buffer_b;
+
+ ret = 0;
+
+out_dec:
+ atomic_dec(&cpu_buffer_a->record_disabled);
+ atomic_dec(&cpu_buffer_b->record_disabled);
+out:
+ return ret;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
+#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
+
+/**
+ * ring_buffer_alloc_read_page - allocate a page to read from buffer
+ * @buffer: the buffer to allocate for.
+ * @cpu: the cpu buffer to allocate.
+ *
+ * This function is used in conjunction with ring_buffer_read_page.
+ * When reading a full page from the ring buffer, these functions
+ * can be used to speed up the process. The calling function should
+ * allocate a few pages first with this function. Then when it
+ * needs to get pages from the ring buffer, it passes the result
+ * of this function into ring_buffer_read_page, which will swap
+ * the page that was allocated, with the read page of the buffer.
+ *
+ * Returns:
+ * The page allocated, or NULL on error.
+ */
+void *ring_buffer_alloc_read_page(struct ring_buffer *buffer, int cpu)
+{
+ struct buffer_data_page *bpage;
+ struct page *page;
+
+ page = alloc_pages_node(cpu_to_node(cpu),
+ GFP_KERNEL | __GFP_NORETRY, 0);
+ if (!page)
+ return NULL;
+
+ bpage = page_address(page);
+
+ rb_init_page(bpage);
+
+ return bpage;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
+
+/**
+ * ring_buffer_free_read_page - free an allocated read page
+ * @buffer: the buffer the page was allocate for
+ * @data: the page to free
+ *
+ * Free a page allocated from ring_buffer_alloc_read_page.
+ */
+void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data)
+{
+ free_page((unsigned long)data);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
+
+/**
+ * ring_buffer_read_page - extract a page from the ring buffer
+ * @buffer: buffer to extract from
+ * @data_page: the page to use allocated from ring_buffer_alloc_read_page
+ * @len: amount to extract
+ * @cpu: the cpu of the buffer to extract
+ * @full: should the extraction only happen when the page is full.
+ *
+ * This function will pull out a page from the ring buffer and consume it.
+ * @data_page must be the address of the variable that was returned
+ * from ring_buffer_alloc_read_page. This is because the page might be used
+ * to swap with a page in the ring buffer.
+ *
+ * for example:
+ * rpage = ring_buffer_alloc_read_page(buffer, cpu);
+ * if (!rpage)
+ * return error;
+ * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
+ * if (ret >= 0)
+ * process_page(rpage, ret);
+ *
+ * When @full is set, the function will not return true unless
+ * the writer is off the reader page.
+ *
+ * Note: it is up to the calling functions to handle sleeps and wakeups.
+ * The ring buffer can be used anywhere in the kernel and can not
+ * blindly call wake_up. The layer that uses the ring buffer must be
+ * responsible for that.
+ *
+ * Returns:
+ * >=0 if data has been transferred, returns the offset of consumed data.
+ * <0 if no data has been transferred.
+ */
+int ring_buffer_read_page(struct ring_buffer *buffer,
+ void **data_page, size_t len, int cpu, int full)
+{
+ struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
+ struct ring_buffer_event *event;
+ struct buffer_data_page *bpage;
+ struct buffer_page *reader;
+ unsigned long missed_events;
+ unsigned long flags;
+ unsigned int commit;
+ unsigned int read;
+ u64 save_timestamp;
+ int ret = -1;
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ goto out;
+
+ /*
+ * If len is not big enough to hold the page header, then
+ * we can not copy anything.
+ */
+ if (len <= BUF_PAGE_HDR_SIZE)
+ goto out;
+
+ len -= BUF_PAGE_HDR_SIZE;
+
+ if (!data_page)
+ goto out;
+
+ bpage = *data_page;
+ if (!bpage)
+ goto out;
+
+ raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+
+ reader = rb_get_reader_page(cpu_buffer);
+ if (!reader)
+ goto out_unlock;
+
+ event = rb_reader_event(cpu_buffer);
+
+ read = reader->read;
+ commit = rb_page_commit(reader);
+
+ /* Check if any events were dropped */
+ missed_events = cpu_buffer->lost_events;
+
+ /*
+ * If this page has been partially read or
+ * if len is not big enough to read the rest of the page or
+ * a writer is still on the page, then
+ * we must copy the data from the page to the buffer.
+ * Otherwise, we can simply swap the page with the one passed in.
+ */
+ if (read || (len < (commit - read)) ||
+ cpu_buffer->reader_page == cpu_buffer->commit_page) {
+ struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
+ unsigned int rpos = read;
+ unsigned int pos = 0;
+ unsigned int size;
+
+ if (full)
+ goto out_unlock;
+
+ if (len > (commit - read))
+ len = (commit - read);
+
+ /* Always keep the time extend and data together */
+ size = rb_event_ts_length(event);
+
+ if (len < size)
+ goto out_unlock;
+
+ /* save the current timestamp, since the user will need it */
+ save_timestamp = cpu_buffer->read_stamp;
+
+ /* Need to copy one event at a time */
+ do {
+ /* We need the size of one event, because
+ * rb_advance_reader only advances by one event,
+ * whereas rb_event_ts_length may include the size of
+ * one or two events.
+ * We have already ensured there's enough space if this
+ * is a time extend. */
+ size = rb_event_length(event);
+ memcpy(bpage->data + pos, rpage->data + rpos, size);
+
+ len -= size;
+
+ rb_advance_reader(cpu_buffer);
+ rpos = reader->read;
+ pos += size;
+
+ if (rpos >= commit)
+ break;
+
+ event = rb_reader_event(cpu_buffer);
+ /* Always keep the time extend and data together */
+ size = rb_event_ts_length(event);
+ } while (len >= size);
+
+ /* update bpage */
+ local_set(&bpage->commit, pos);
+ bpage->time_stamp = save_timestamp;
+
+ /* we copied everything to the beginning */
+ read = 0;
+ } else {
+ /* update the entry counter */
+ cpu_buffer->read += rb_page_entries(reader);
+ cpu_buffer->read_bytes += BUF_PAGE_SIZE;
+
+ /* swap the pages */
+ rb_init_page(bpage);
+ bpage = reader->page;
+ reader->page = *data_page;
+ local_set(&reader->write, 0);
+ local_set(&reader->entries, 0);
+ reader->read = 0;
+ *data_page = bpage;
+
+ /*
+ * Use the real_end for the data size,
+ * This gives us a chance to store the lost events
+ * on the page.
+ */
+ if (reader->real_end)
+ local_set(&bpage->commit, reader->real_end);
+ }
+ ret = read;
+
+ cpu_buffer->lost_events = 0;
+
+ commit = local_read(&bpage->commit);
+ /*
+ * Set a flag in the commit field if we lost events
+ */
+ if (missed_events) {
+ /* If there is room at the end of the page to save the
+ * missed events, then record it there.
+ */
+ if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) {
+ memcpy(&bpage->data[commit], &missed_events,
+ sizeof(missed_events));
+ local_add(RB_MISSED_STORED, &bpage->commit);
+ commit += sizeof(missed_events);
+ }
+ local_add(RB_MISSED_EVENTS, &bpage->commit);
+ }
+
+ /*
+ * This page may be off to user land. Zero it out here.
+ */
+ if (commit < BUF_PAGE_SIZE)
+ memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit);
+
+ out_unlock:
+ raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+
+ out:
+ return ret;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_read_page);
+
+#ifdef CONFIG_HOTPLUG_CPU
+static int rb_cpu_notify(struct notifier_block *self,
+ unsigned long action, void *hcpu)
+{
+ struct ring_buffer *buffer =
+ container_of(self, struct ring_buffer, cpu_notify);
+ long cpu = (long)hcpu;
+ int cpu_i, nr_pages_same;
+ unsigned int nr_pages;
+
+ switch (action) {
+ case CPU_UP_PREPARE:
+ case CPU_UP_PREPARE_FROZEN:
+ if (cpumask_test_cpu(cpu, buffer->cpumask))
+ return NOTIFY_OK;
+
+ nr_pages = 0;
+ nr_pages_same = 1;
+ /* check if all cpu sizes are same */
+ for_each_buffer_cpu(buffer, cpu_i) {
+ /* fill in the size from first enabled cpu */
+ if (nr_pages == 0)
+ nr_pages = buffer->buffers[cpu_i]->nr_pages;
+ if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
+ nr_pages_same = 0;
+ break;
+ }
+ }
+ /* allocate minimum pages, user can later expand it */
+ if (!nr_pages_same)
+ nr_pages = 2;
+ buffer->buffers[cpu] =
+ rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
+ if (!buffer->buffers[cpu]) {
+ WARN(1, "failed to allocate ring buffer on CPU %ld\n",
+ cpu);
+ return NOTIFY_OK;
+ }
+ smp_wmb();
+ cpumask_set_cpu(cpu, buffer->cpumask);
+ break;
+ case CPU_DOWN_PREPARE:
+ case CPU_DOWN_PREPARE_FROZEN:
+ /*
+ * Do nothing.
+ * If we were to free the buffer, then the user would
+ * lose any trace that was in the buffer.
+ */
+ break;
+ default:
+ break;
+ }
+ return NOTIFY_OK;
+}
+#endif
+
+#ifdef CONFIG_RING_BUFFER_STARTUP_TEST
+/*
+ * This is a basic integrity check of the ring buffer.
+ * Late in the boot cycle this test will run when configured in.
+ * It will kick off a thread per CPU that will go into a loop
+ * writing to the per cpu ring buffer various sizes of data.
+ * Some of the data will be large items, some small.
+ *
+ * Another thread is created that goes into a spin, sending out
+ * IPIs to the other CPUs to also write into the ring buffer.
+ * this is to test the nesting ability of the buffer.
+ *
+ * Basic stats are recorded and reported. If something in the
+ * ring buffer should happen that's not expected, a big warning
+ * is displayed and all ring buffers are disabled.
+ */
+static struct task_struct *rb_threads[NR_CPUS] __initdata;
+
+struct rb_test_data {
+ struct ring_buffer *buffer;
+ unsigned long events;
+ unsigned long bytes_written;
+ unsigned long bytes_alloc;
+ unsigned long bytes_dropped;
+ unsigned long events_nested;
+ unsigned long bytes_written_nested;
+ unsigned long bytes_alloc_nested;
+ unsigned long bytes_dropped_nested;
+ int min_size_nested;
+ int max_size_nested;
+ int max_size;
+ int min_size;
+ int cpu;
+ int cnt;
+};
+
+static struct rb_test_data rb_data[NR_CPUS] __initdata;
+
+/* 1 meg per cpu */
+#define RB_TEST_BUFFER_SIZE 1048576
+
+static char rb_string[] __initdata =
+ "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
+ "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
+ "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
+
+static bool rb_test_started __initdata;
+
+struct rb_item {
+ int size;
+ char str[];
+};
+
+static __init int rb_write_something(struct rb_test_data *data, bool nested)
+{
+ struct ring_buffer_event *event;
+ struct rb_item *item;
+ bool started;
+ int event_len;
+ int size;
+ int len;
+ int cnt;
+
+ /* Have nested writes different that what is written */
+ cnt = data->cnt + (nested ? 27 : 0);
+
+ /* Multiply cnt by ~e, to make some unique increment */
+ size = (data->cnt * 68 / 25) % (sizeof(rb_string) - 1);
+
+ len = size + sizeof(struct rb_item);
+
+ started = rb_test_started;
+ /* read rb_test_started before checking buffer enabled */
+ smp_rmb();
+
+ event = ring_buffer_lock_reserve(data->buffer, len);
+ if (!event) {
+ /* Ignore dropped events before test starts. */
+ if (started) {
+ if (nested)
+ data->bytes_dropped += len;
+ else
+ data->bytes_dropped_nested += len;
+ }
+ return len;
+ }
+
+ event_len = ring_buffer_event_length(event);
+
+ if (RB_WARN_ON(data->buffer, event_len < len))
+ goto out;
+
+ item = ring_buffer_event_data(event);
+ item->size = size;
+ memcpy(item->str, rb_string, size);
+
+ if (nested) {
+ data->bytes_alloc_nested += event_len;
+ data->bytes_written_nested += len;
+ data->events_nested++;
+ if (!data->min_size_nested || len < data->min_size_nested)
+ data->min_size_nested = len;
+ if (len > data->max_size_nested)
+ data->max_size_nested = len;
+ } else {
+ data->bytes_alloc += event_len;
+ data->bytes_written += len;
+ data->events++;
+ if (!data->min_size || len < data->min_size)
+ data->max_size = len;
+ if (len > data->max_size)
+ data->max_size = len;
+ }
+
+ out:
+ ring_buffer_unlock_commit(data->buffer, event);
+
+ return 0;
+}
+
+static __init int rb_test(void *arg)
+{
+ struct rb_test_data *data = arg;
+
+ while (!kthread_should_stop()) {
+ rb_write_something(data, false);
+ data->cnt++;
+
+ set_current_state(TASK_INTERRUPTIBLE);
+ /* Now sleep between a min of 100-300us and a max of 1ms */
+ usleep_range(((data->cnt % 3) + 1) * 100, 1000);
+ }
+
+ return 0;
+}
+
+static __init void rb_ipi(void *ignore)
+{
+ struct rb_test_data *data;
+ int cpu = smp_processor_id();
+
+ data = &rb_data[cpu];
+ rb_write_something(data, true);
+}
+
+static __init int rb_hammer_test(void *arg)
+{
+ while (!kthread_should_stop()) {
+
+ /* Send an IPI to all cpus to write data! */
+ smp_call_function(rb_ipi, NULL, 1);
+ /* No sleep, but for non preempt, let others run */
+ schedule();
+ }
+
+ return 0;
+}
+
+static __init int test_ringbuffer(void)
+{
+ struct task_struct *rb_hammer;
+ struct ring_buffer *buffer;
+ int cpu;
+ int ret = 0;
+
+ pr_info("Running ring buffer tests...\n");
+
+ buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
+ if (WARN_ON(!buffer))
+ return 0;
+
+ /* Disable buffer so that threads can't write to it yet */
+ ring_buffer_record_off(buffer);
+
+ for_each_online_cpu(cpu) {
+ rb_data[cpu].buffer = buffer;
+ rb_data[cpu].cpu = cpu;
+ rb_data[cpu].cnt = cpu;
+ rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu],
+ "rbtester/%d", cpu);
+ if (WARN_ON(!rb_threads[cpu])) {
+ pr_cont("FAILED\n");
+ ret = -1;
+ goto out_free;
+ }
+
+ kthread_bind(rb_threads[cpu], cpu);
+ wake_up_process(rb_threads[cpu]);
+ }
+
+ /* Now create the rb hammer! */
+ rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
+ if (WARN_ON(!rb_hammer)) {
+ pr_cont("FAILED\n");
+ ret = -1;
+ goto out_free;
+ }
+
+ ring_buffer_record_on(buffer);
+ /*
+ * Show buffer is enabled before setting rb_test_started.
+ * Yes there's a small race window where events could be
+ * dropped and the thread wont catch it. But when a ring
+ * buffer gets enabled, there will always be some kind of
+ * delay before other CPUs see it. Thus, we don't care about
+ * those dropped events. We care about events dropped after
+ * the threads see that the buffer is active.
+ */
+ smp_wmb();
+ rb_test_started = true;
+
+ set_current_state(TASK_INTERRUPTIBLE);
+ /* Just run for 10 seconds */;
+ schedule_timeout(10 * HZ);
+
+ kthread_stop(rb_hammer);
+
+ out_free:
+ for_each_online_cpu(cpu) {
+ if (!rb_threads[cpu])
+ break;
+ kthread_stop(rb_threads[cpu]);
+ }
+ if (ret) {
+ ring_buffer_free(buffer);
+ return ret;
+ }
+
+ /* Report! */
+ pr_info("finished\n");
+ for_each_online_cpu(cpu) {
+ struct ring_buffer_event *event;
+ struct rb_test_data *data = &rb_data[cpu];
+ struct rb_item *item;
+ unsigned long total_events;
+ unsigned long total_dropped;
+ unsigned long total_written;
+ unsigned long total_alloc;
+ unsigned long total_read = 0;
+ unsigned long total_size = 0;
+ unsigned long total_len = 0;
+ unsigned long total_lost = 0;
+ unsigned long lost;
+ int big_event_size;
+ int small_event_size;
+
+ ret = -1;
+
+ total_events = data->events + data->events_nested;
+ total_written = data->bytes_written + data->bytes_written_nested;
+ total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
+ total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
+
+ big_event_size = data->max_size + data->max_size_nested;
+ small_event_size = data->min_size + data->min_size_nested;
+
+ pr_info("CPU %d:\n", cpu);
+ pr_info(" events: %ld\n", total_events);
+ pr_info(" dropped bytes: %ld\n", total_dropped);
+ pr_info(" alloced bytes: %ld\n", total_alloc);
+ pr_info(" written bytes: %ld\n", total_written);
+ pr_info(" biggest event: %d\n", big_event_size);
+ pr_info(" smallest event: %d\n", small_event_size);
+
+ if (RB_WARN_ON(buffer, total_dropped))
+ break;
+
+ ret = 0;
+
+ while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
+ total_lost += lost;
+ item = ring_buffer_event_data(event);
+ total_len += ring_buffer_event_length(event);
+ total_size += item->size + sizeof(struct rb_item);
+ if (memcmp(&item->str[0], rb_string, item->size) != 0) {
+ pr_info("FAILED!\n");
+ pr_info("buffer had: %.*s\n", item->size, item->str);
+ pr_info("expected: %.*s\n", item->size, rb_string);
+ RB_WARN_ON(buffer, 1);
+ ret = -1;
+ break;
+ }
+ total_read++;
+ }
+ if (ret)
+ break;
+
+ ret = -1;
+
+ pr_info(" read events: %ld\n", total_read);
+ pr_info(" lost events: %ld\n", total_lost);
+ pr_info(" total events: %ld\n", total_lost + total_read);
+ pr_info(" recorded len bytes: %ld\n", total_len);
+ pr_info(" recorded size bytes: %ld\n", total_size);
+ if (total_lost)
+ pr_info(" With dropped events, record len and size may not match\n"
+ " alloced and written from above\n");
+ if (!total_lost) {
+ if (RB_WARN_ON(buffer, total_len != total_alloc ||
+ total_size != total_written))
+ break;
+ }
+ if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
+ break;
+
+ ret = 0;
+ }
+ if (!ret)
+ pr_info("Ring buffer PASSED!\n");
+
+ ring_buffer_free(buffer);
+ return 0;
+}
+
+late_initcall(test_ringbuffer);
+#endif /* CONFIG_RING_BUFFER_STARTUP_TEST */
Code Review / kvmfornfv.git / blobdiff