--- /dev/null
+/*
+ * Sleepable Read-Copy Update mechanism for mutual exclusion
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, you can access it online at
+ * http://www.gnu.org/licenses/gpl-2.0.html.
+ *
+ * Copyright (C) IBM Corporation, 2006
+ * Copyright (C) Fujitsu, 2012
+ *
+ * Author: Paul McKenney <paulmck@us.ibm.com>
+ * Lai Jiangshan <laijs@cn.fujitsu.com>
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ * Documentation/RCU/ *.txt
+ *
+ */
+
+#ifndef _LINUX_SRCU_H
+#define _LINUX_SRCU_H
+
+#include <linux/mutex.h>
+#include <linux/rcupdate.h>
+#include <linux/workqueue.h>
+
+struct srcu_struct_array {
+ unsigned long c[2];
+ unsigned long seq[2];
+};
+
+struct rcu_batch {
+ struct rcu_head *head, **tail;
+};
+
+#define RCU_BATCH_INIT(name) { NULL, &(name.head) }
+
+struct srcu_struct {
+ unsigned long completed;
+ struct srcu_struct_array __percpu *per_cpu_ref;
+ spinlock_t queue_lock; /* protect ->batch_queue, ->running */
+ bool running;
+ /* callbacks just queued */
+ struct rcu_batch batch_queue;
+ /* callbacks try to do the first check_zero */
+ struct rcu_batch batch_check0;
+ /* callbacks done with the first check_zero and the flip */
+ struct rcu_batch batch_check1;
+ struct rcu_batch batch_done;
+ struct delayed_work work;
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ struct lockdep_map dep_map;
+#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+};
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+
+int __init_srcu_struct(struct srcu_struct *sp, const char *name,
+ struct lock_class_key *key);
+
+#define init_srcu_struct(sp) \
+({ \
+ static struct lock_class_key __srcu_key; \
+ \
+ __init_srcu_struct((sp), #sp, &__srcu_key); \
+})
+
+#define __SRCU_DEP_MAP_INIT(srcu_name) .dep_map = { .name = #srcu_name },
+#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+
+int init_srcu_struct(struct srcu_struct *sp);
+
+#define __SRCU_DEP_MAP_INIT(srcu_name)
+#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+
+void process_srcu(struct work_struct *work);
+
+#define __SRCU_STRUCT_INIT(name, pcpu_name) \
+ { \
+ .completed = -300, \
+ .per_cpu_ref = &pcpu_name, \
+ .queue_lock = __SPIN_LOCK_UNLOCKED(name.queue_lock), \
+ .running = false, \
+ .batch_queue = RCU_BATCH_INIT(name.batch_queue), \
+ .batch_check0 = RCU_BATCH_INIT(name.batch_check0), \
+ .batch_check1 = RCU_BATCH_INIT(name.batch_check1), \
+ .batch_done = RCU_BATCH_INIT(name.batch_done), \
+ .work = __DELAYED_WORK_INITIALIZER(name.work, process_srcu, 0),\
+ __SRCU_DEP_MAP_INIT(name) \
+ }
+
+/*
+ * define and init a srcu struct at build time.
+ * dont't call init_srcu_struct() nor cleanup_srcu_struct() on it.
+ */
+#define __DEFINE_SRCU(name, is_static) \
+ static DEFINE_PER_CPU(struct srcu_struct_array, name##_srcu_array);\
+ is_static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name##_srcu_array)
+#define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */)
+#define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static)
+
+/**
+ * call_srcu() - Queue a callback for invocation after an SRCU grace period
+ * @sp: srcu_struct in queue the callback
+ * @head: structure to be used for queueing the SRCU callback.
+ * @func: function to be invoked after the SRCU grace period
+ *
+ * The callback function will be invoked some time after a full SRCU
+ * grace period elapses, in other words after all pre-existing SRCU
+ * read-side critical sections have completed. However, the callback
+ * function might well execute concurrently with other SRCU read-side
+ * critical sections that started after call_srcu() was invoked. SRCU
+ * read-side critical sections are delimited by srcu_read_lock() and
+ * srcu_read_unlock(), and may be nested.
+ *
+ * The callback will be invoked from process context, but must nevertheless
+ * be fast and must not block.
+ */
+void call_srcu(struct srcu_struct *sp, struct rcu_head *head,
+ void (*func)(struct rcu_head *head));
+
+void cleanup_srcu_struct(struct srcu_struct *sp);
+int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
+void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
+void synchronize_srcu(struct srcu_struct *sp);
+void synchronize_srcu_expedited(struct srcu_struct *sp);
+unsigned long srcu_batches_completed(struct srcu_struct *sp);
+void srcu_barrier(struct srcu_struct *sp);
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+
+/**
+ * srcu_read_lock_held - might we be in SRCU read-side critical section?
+ *
+ * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU
+ * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC,
+ * this assumes we are in an SRCU read-side critical section unless it can
+ * prove otherwise.
+ *
+ * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
+ * and while lockdep is disabled.
+ *
+ * Note that SRCU is based on its own statemachine and it doesn't
+ * relies on normal RCU, it can be called from the CPU which
+ * is in the idle loop from an RCU point of view or offline.
+ */
+static inline int srcu_read_lock_held(struct srcu_struct *sp)
+{
+ if (!debug_lockdep_rcu_enabled())
+ return 1;
+ return lock_is_held(&sp->dep_map);
+}
+
+#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+
+static inline int srcu_read_lock_held(struct srcu_struct *sp)
+{
+ return 1;
+}
+
+#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+
+/**
+ * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing
+ * @p: the pointer to fetch and protect for later dereferencing
+ * @sp: pointer to the srcu_struct, which is used to check that we
+ * really are in an SRCU read-side critical section.
+ * @c: condition to check for update-side use
+ *
+ * If PROVE_RCU is enabled, invoking this outside of an RCU read-side
+ * critical section will result in an RCU-lockdep splat, unless @c evaluates
+ * to 1. The @c argument will normally be a logical expression containing
+ * lockdep_is_held() calls.
+ */
+#define srcu_dereference_check(p, sp, c) \
+ __rcu_dereference_check((p), (c) || srcu_read_lock_held(sp), __rcu)
+
+/**
+ * srcu_dereference - fetch SRCU-protected pointer for later dereferencing
+ * @p: the pointer to fetch and protect for later dereferencing
+ * @sp: pointer to the srcu_struct, which is used to check that we
+ * really are in an SRCU read-side critical section.
+ *
+ * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU
+ * is enabled, invoking this outside of an RCU read-side critical
+ * section will result in an RCU-lockdep splat.
+ */
+#define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0)
+
+/**
+ * srcu_read_lock - register a new reader for an SRCU-protected structure.
+ * @sp: srcu_struct in which to register the new reader.
+ *
+ * Enter an SRCU read-side critical section. Note that SRCU read-side
+ * critical sections may be nested. However, it is illegal to
+ * call anything that waits on an SRCU grace period for the same
+ * srcu_struct, whether directly or indirectly. Please note that
+ * one way to indirectly wait on an SRCU grace period is to acquire
+ * a mutex that is held elsewhere while calling synchronize_srcu() or
+ * synchronize_srcu_expedited().
+ *
+ * Note that srcu_read_lock() and the matching srcu_read_unlock() must
+ * occur in the same context, for example, it is illegal to invoke
+ * srcu_read_unlock() in an irq handler if the matching srcu_read_lock()
+ * was invoked in process context.
+ */
+static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
+{
+ int retval = __srcu_read_lock(sp);
+
+ rcu_lock_acquire(&(sp)->dep_map);
+ return retval;
+}
+
+/**
+ * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
+ * @sp: srcu_struct in which to unregister the old reader.
+ * @idx: return value from corresponding srcu_read_lock().
+ *
+ * Exit an SRCU read-side critical section.
+ */
+static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
+ __releases(sp)
+{
+ rcu_lock_release(&(sp)->dep_map);
+ __srcu_read_unlock(sp, idx);
+}
+
+/**
+ * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock
+ *
+ * Converts the preceding srcu_read_unlock into a two-way memory barrier.
+ *
+ * Call this after srcu_read_unlock, to guarantee that all memory operations
+ * that occur after smp_mb__after_srcu_read_unlock will appear to happen after
+ * the preceding srcu_read_unlock.
+ */
+static inline void smp_mb__after_srcu_read_unlock(void)
+{
+ /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */
+}
+
+#endif
Code Review / kvmfornfv.git / blobdiff