--- /dev/null
+/**
+ * @file buffer_sync.c
+ *
+ * @remark Copyright 2002-2009 OProfile authors
+ * @remark Read the file COPYING
+ *
+ * @author John Levon <levon@movementarian.org>
+ * @author Barry Kasindorf
+ * @author Robert Richter <robert.richter@amd.com>
+ *
+ * This is the core of the buffer management. Each
+ * CPU buffer is processed and entered into the
+ * global event buffer. Such processing is necessary
+ * in several circumstances, mentioned below.
+ *
+ * The processing does the job of converting the
+ * transitory EIP value into a persistent dentry/offset
+ * value that the profiler can record at its leisure.
+ *
+ * See fs/dcookies.c for a description of the dentry/offset
+ * objects.
+ */
+
+#include <linux/file.h>
+#include <linux/mm.h>
+#include <linux/workqueue.h>
+#include <linux/notifier.h>
+#include <linux/dcookies.h>
+#include <linux/profile.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/oprofile.h>
+#include <linux/sched.h>
+#include <linux/gfp.h>
+
+#include "oprofile_stats.h"
+#include "event_buffer.h"
+#include "cpu_buffer.h"
+#include "buffer_sync.h"
+
+static LIST_HEAD(dying_tasks);
+static LIST_HEAD(dead_tasks);
+static cpumask_var_t marked_cpus;
+static DEFINE_SPINLOCK(task_mortuary);
+static void process_task_mortuary(void);
+
+/* Take ownership of the task struct and place it on the
+ * list for processing. Only after two full buffer syncs
+ * does the task eventually get freed, because by then
+ * we are sure we will not reference it again.
+ * Can be invoked from softirq via RCU callback due to
+ * call_rcu() of the task struct, hence the _irqsave.
+ */
+static int
+task_free_notify(struct notifier_block *self, unsigned long val, void *data)
+{
+ unsigned long flags;
+ struct task_struct *task = data;
+ spin_lock_irqsave(&task_mortuary, flags);
+ list_add(&task->tasks, &dying_tasks);
+ spin_unlock_irqrestore(&task_mortuary, flags);
+ return NOTIFY_OK;
+}
+
+
+/* The task is on its way out. A sync of the buffer means we can catch
+ * any remaining samples for this task.
+ */
+static int
+task_exit_notify(struct notifier_block *self, unsigned long val, void *data)
+{
+ /* To avoid latency problems, we only process the current CPU,
+ * hoping that most samples for the task are on this CPU
+ */
+ sync_buffer(raw_smp_processor_id());
+ return 0;
+}
+
+
+/* The task is about to try a do_munmap(). We peek at what it's going to
+ * do, and if it's an executable region, process the samples first, so
+ * we don't lose any. This does not have to be exact, it's a QoI issue
+ * only.
+ */
+static int
+munmap_notify(struct notifier_block *self, unsigned long val, void *data)
+{
+ unsigned long addr = (unsigned long)data;
+ struct mm_struct *mm = current->mm;
+ struct vm_area_struct *mpnt;
+
+ down_read(&mm->mmap_sem);
+
+ mpnt = find_vma(mm, addr);
+ if (mpnt && mpnt->vm_file && (mpnt->vm_flags & VM_EXEC)) {
+ up_read(&mm->mmap_sem);
+ /* To avoid latency problems, we only process the current CPU,
+ * hoping that most samples for the task are on this CPU
+ */
+ sync_buffer(raw_smp_processor_id());
+ return 0;
+ }
+
+ up_read(&mm->mmap_sem);
+ return 0;
+}
+
+
+/* We need to be told about new modules so we don't attribute to a previously
+ * loaded module, or drop the samples on the floor.
+ */
+static int
+module_load_notify(struct notifier_block *self, unsigned long val, void *data)
+{
+#ifdef CONFIG_MODULES
+ if (val != MODULE_STATE_COMING)
+ return 0;
+
+ /* FIXME: should we process all CPU buffers ? */
+ mutex_lock(&buffer_mutex);
+ add_event_entry(ESCAPE_CODE);
+ add_event_entry(MODULE_LOADED_CODE);
+ mutex_unlock(&buffer_mutex);
+#endif
+ return 0;
+}
+
+
+static struct notifier_block task_free_nb = {
+ .notifier_call = task_free_notify,
+};
+
+static struct notifier_block task_exit_nb = {
+ .notifier_call = task_exit_notify,
+};
+
+static struct notifier_block munmap_nb = {
+ .notifier_call = munmap_notify,
+};
+
+static struct notifier_block module_load_nb = {
+ .notifier_call = module_load_notify,
+};
+
+static void free_all_tasks(void)
+{
+ /* make sure we don't leak task structs */
+ process_task_mortuary();
+ process_task_mortuary();
+}
+
+int sync_start(void)
+{
+ int err;
+
+ if (!zalloc_cpumask_var(&marked_cpus, GFP_KERNEL))
+ return -ENOMEM;
+
+ err = task_handoff_register(&task_free_nb);
+ if (err)
+ goto out1;
+ err = profile_event_register(PROFILE_TASK_EXIT, &task_exit_nb);
+ if (err)
+ goto out2;
+ err = profile_event_register(PROFILE_MUNMAP, &munmap_nb);
+ if (err)
+ goto out3;
+ err = register_module_notifier(&module_load_nb);
+ if (err)
+ goto out4;
+
+ start_cpu_work();
+
+out:
+ return err;
+out4:
+ profile_event_unregister(PROFILE_MUNMAP, &munmap_nb);
+out3:
+ profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb);
+out2:
+ task_handoff_unregister(&task_free_nb);
+ free_all_tasks();
+out1:
+ free_cpumask_var(marked_cpus);
+ goto out;
+}
+
+
+void sync_stop(void)
+{
+ end_cpu_work();
+ unregister_module_notifier(&module_load_nb);
+ profile_event_unregister(PROFILE_MUNMAP, &munmap_nb);
+ profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb);
+ task_handoff_unregister(&task_free_nb);
+ barrier(); /* do all of the above first */
+
+ flush_cpu_work();
+
+ free_all_tasks();
+ free_cpumask_var(marked_cpus);
+}
+
+
+/* Optimisation. We can manage without taking the dcookie sem
+ * because we cannot reach this code without at least one
+ * dcookie user still being registered (namely, the reader
+ * of the event buffer). */
+static inline unsigned long fast_get_dcookie(struct path *path)
+{
+ unsigned long cookie;
+
+ if (path->dentry->d_flags & DCACHE_COOKIE)
+ return (unsigned long)path->dentry;
+ get_dcookie(path, &cookie);
+ return cookie;
+}
+
+
+/* Look up the dcookie for the task's mm->exe_file,
+ * which corresponds loosely to "application name". This is
+ * not strictly necessary but allows oprofile to associate
+ * shared-library samples with particular applications
+ */
+static unsigned long get_exec_dcookie(struct mm_struct *mm)
+{
+ unsigned long cookie = NO_COOKIE;
+ struct file *exe_file;
+
+ if (!mm)
+ goto done;
+
+ exe_file = get_mm_exe_file(mm);
+ if (!exe_file)
+ goto done;
+
+ cookie = fast_get_dcookie(&exe_file->f_path);
+ fput(exe_file);
+done:
+ return cookie;
+}
+
+
+/* Convert the EIP value of a sample into a persistent dentry/offset
+ * pair that can then be added to the global event buffer. We make
+ * sure to do this lookup before a mm->mmap modification happens so
+ * we don't lose track.
+ *
+ * The caller must ensure the mm is not nil (ie: not a kernel thread).
+ */
+static unsigned long
+lookup_dcookie(struct mm_struct *mm, unsigned long addr, off_t *offset)
+{
+ unsigned long cookie = NO_COOKIE;
+ struct vm_area_struct *vma;
+
+ down_read(&mm->mmap_sem);
+ for (vma = find_vma(mm, addr); vma; vma = vma->vm_next) {
+
+ if (addr < vma->vm_start || addr >= vma->vm_end)
+ continue;
+
+ if (vma->vm_file) {
+ cookie = fast_get_dcookie(&vma->vm_file->f_path);
+ *offset = (vma->vm_pgoff << PAGE_SHIFT) + addr -
+ vma->vm_start;
+ } else {
+ /* must be an anonymous map */
+ *offset = addr;
+ }
+
+ break;
+ }
+
+ if (!vma)
+ cookie = INVALID_COOKIE;
+ up_read(&mm->mmap_sem);
+
+ return cookie;
+}
+
+static unsigned long last_cookie = INVALID_COOKIE;
+
+static void add_cpu_switch(int i)
+{
+ add_event_entry(ESCAPE_CODE);
+ add_event_entry(CPU_SWITCH_CODE);
+ add_event_entry(i);
+ last_cookie = INVALID_COOKIE;
+}
+
+static void add_kernel_ctx_switch(unsigned int in_kernel)
+{
+ add_event_entry(ESCAPE_CODE);
+ if (in_kernel)
+ add_event_entry(KERNEL_ENTER_SWITCH_CODE);
+ else
+ add_event_entry(KERNEL_EXIT_SWITCH_CODE);
+}
+
+static void
+add_user_ctx_switch(struct task_struct const *task, unsigned long cookie)
+{
+ add_event_entry(ESCAPE_CODE);
+ add_event_entry(CTX_SWITCH_CODE);
+ add_event_entry(task->pid);
+ add_event_entry(cookie);
+ /* Another code for daemon back-compat */
+ add_event_entry(ESCAPE_CODE);
+ add_event_entry(CTX_TGID_CODE);
+ add_event_entry(task->tgid);
+}
+
+
+static void add_cookie_switch(unsigned long cookie)
+{
+ add_event_entry(ESCAPE_CODE);
+ add_event_entry(COOKIE_SWITCH_CODE);
+ add_event_entry(cookie);
+}
+
+
+static void add_trace_begin(void)
+{
+ add_event_entry(ESCAPE_CODE);
+ add_event_entry(TRACE_BEGIN_CODE);
+}
+
+static void add_data(struct op_entry *entry, struct mm_struct *mm)
+{
+ unsigned long code, pc, val;
+ unsigned long cookie;
+ off_t offset;
+
+ if (!op_cpu_buffer_get_data(entry, &code))
+ return;
+ if (!op_cpu_buffer_get_data(entry, &pc))
+ return;
+ if (!op_cpu_buffer_get_size(entry))
+ return;
+
+ if (mm) {
+ cookie = lookup_dcookie(mm, pc, &offset);
+
+ if (cookie == NO_COOKIE)
+ offset = pc;
+ if (cookie == INVALID_COOKIE) {
+ atomic_inc(&oprofile_stats.sample_lost_no_mapping);
+ offset = pc;
+ }
+ if (cookie != last_cookie) {
+ add_cookie_switch(cookie);
+ last_cookie = cookie;
+ }
+ } else
+ offset = pc;
+
+ add_event_entry(ESCAPE_CODE);
+ add_event_entry(code);
+ add_event_entry(offset); /* Offset from Dcookie */
+
+ while (op_cpu_buffer_get_data(entry, &val))
+ add_event_entry(val);
+}
+
+static inline void add_sample_entry(unsigned long offset, unsigned long event)
+{
+ add_event_entry(offset);
+ add_event_entry(event);
+}
+
+
+/*
+ * Add a sample to the global event buffer. If possible the
+ * sample is converted into a persistent dentry/offset pair
+ * for later lookup from userspace. Return 0 on failure.
+ */
+static int
+add_sample(struct mm_struct *mm, struct op_sample *s, int in_kernel)
+{
+ unsigned long cookie;
+ off_t offset;
+
+ if (in_kernel) {
+ add_sample_entry(s->eip, s->event);
+ return 1;
+ }
+
+ /* add userspace sample */
+
+ if (!mm) {
+ atomic_inc(&oprofile_stats.sample_lost_no_mm);
+ return 0;
+ }
+
+ cookie = lookup_dcookie(mm, s->eip, &offset);
+
+ if (cookie == INVALID_COOKIE) {
+ atomic_inc(&oprofile_stats.sample_lost_no_mapping);
+ return 0;
+ }
+
+ if (cookie != last_cookie) {
+ add_cookie_switch(cookie);
+ last_cookie = cookie;
+ }
+
+ add_sample_entry(offset, s->event);
+
+ return 1;
+}
+
+
+static void release_mm(struct mm_struct *mm)
+{
+ if (!mm)
+ return;
+ mmput(mm);
+}
+
+static inline int is_code(unsigned long val)
+{
+ return val == ESCAPE_CODE;
+}
+
+
+/* Move tasks along towards death. Any tasks on dead_tasks
+ * will definitely have no remaining references in any
+ * CPU buffers at this point, because we use two lists,
+ * and to have reached the list, it must have gone through
+ * one full sync already.
+ */
+static void process_task_mortuary(void)
+{
+ unsigned long flags;
+ LIST_HEAD(local_dead_tasks);
+ struct task_struct *task;
+ struct task_struct *ttask;
+
+ spin_lock_irqsave(&task_mortuary, flags);
+
+ list_splice_init(&dead_tasks, &local_dead_tasks);
+ list_splice_init(&dying_tasks, &dead_tasks);
+
+ spin_unlock_irqrestore(&task_mortuary, flags);
+
+ list_for_each_entry_safe(task, ttask, &local_dead_tasks, tasks) {
+ list_del(&task->tasks);
+ free_task(task);
+ }
+}
+
+
+static void mark_done(int cpu)
+{
+ int i;
+
+ cpumask_set_cpu(cpu, marked_cpus);
+
+ for_each_online_cpu(i) {
+ if (!cpumask_test_cpu(i, marked_cpus))
+ return;
+ }
+
+ /* All CPUs have been processed at least once,
+ * we can process the mortuary once
+ */
+ process_task_mortuary();
+
+ cpumask_clear(marked_cpus);
+}
+
+
+/* FIXME: this is not sufficient if we implement syscall barrier backtrace
+ * traversal, the code switch to sb_sample_start at first kernel enter/exit
+ * switch so we need a fifth state and some special handling in sync_buffer()
+ */
+typedef enum {
+ sb_bt_ignore = -2,
+ sb_buffer_start,
+ sb_bt_start,
+ sb_sample_start,
+} sync_buffer_state;
+
+/* Sync one of the CPU's buffers into the global event buffer.
+ * Here we need to go through each batch of samples punctuated
+ * by context switch notes, taking the task's mmap_sem and doing
+ * lookup in task->mm->mmap to convert EIP into dcookie/offset
+ * value.
+ */
+void sync_buffer(int cpu)
+{
+ struct mm_struct *mm = NULL;
+ struct mm_struct *oldmm;
+ unsigned long val;
+ struct task_struct *new;
+ unsigned long cookie = 0;
+ int in_kernel = 1;
+ sync_buffer_state state = sb_buffer_start;
+ unsigned int i;
+ unsigned long available;
+ unsigned long flags;
+ struct op_entry entry;
+ struct op_sample *sample;
+
+ mutex_lock(&buffer_mutex);
+
+ add_cpu_switch(cpu);
+
+ op_cpu_buffer_reset(cpu);
+ available = op_cpu_buffer_entries(cpu);
+
+ for (i = 0; i < available; ++i) {
+ sample = op_cpu_buffer_read_entry(&entry, cpu);
+ if (!sample)
+ break;
+
+ if (is_code(sample->eip)) {
+ flags = sample->event;
+ if (flags & TRACE_BEGIN) {
+ state = sb_bt_start;
+ add_trace_begin();
+ }
+ if (flags & KERNEL_CTX_SWITCH) {
+ /* kernel/userspace switch */
+ in_kernel = flags & IS_KERNEL;
+ if (state == sb_buffer_start)
+ state = sb_sample_start;
+ add_kernel_ctx_switch(flags & IS_KERNEL);
+ }
+ if (flags & USER_CTX_SWITCH
+ && op_cpu_buffer_get_data(&entry, &val)) {
+ /* userspace context switch */
+ new = (struct task_struct *)val;
+ oldmm = mm;
+ release_mm(oldmm);
+ mm = get_task_mm(new);
+ if (mm != oldmm)
+ cookie = get_exec_dcookie(mm);
+ add_user_ctx_switch(new, cookie);
+ }
+ if (op_cpu_buffer_get_size(&entry))
+ add_data(&entry, mm);
+ continue;
+ }
+
+ if (state < sb_bt_start)
+ /* ignore sample */
+ continue;
+
+ if (add_sample(mm, sample, in_kernel))
+ continue;
+
+ /* ignore backtraces if failed to add a sample */
+ if (state == sb_bt_start) {
+ state = sb_bt_ignore;
+ atomic_inc(&oprofile_stats.bt_lost_no_mapping);
+ }
+ }
+ release_mm(mm);
+
+ mark_done(cpu);
+
+ mutex_unlock(&buffer_mutex);
+}
+
+/* The function can be used to add a buffer worth of data directly to
+ * the kernel buffer. The buffer is assumed to be a circular buffer.
+ * Take the entries from index start and end at index end, wrapping
+ * at max_entries.
+ */
+void oprofile_put_buff(unsigned long *buf, unsigned int start,
+ unsigned int stop, unsigned int max)
+{
+ int i;
+
+ i = start;
+
+ mutex_lock(&buffer_mutex);
+ while (i != stop) {
+ add_event_entry(buf[i++]);
+
+ if (i >= max)
+ i = 0;
+ }
+
+ mutex_unlock(&buffer_mutex);
+}
+
Code Review / kvmfornfv.git / blobdiff