};
/* Exported common interfaces */
-extern void synchronize_rcu_bh(void);
-extern void synchronize_sched(void);
extern void rcu_barrier(void);
extern void rcu_barrier_bh(void);
extern void rcu_barrier_sched(void);
/* Internal to kernel */
extern void rcu_init(void);
-extern int rcu_scheduler_active;
-extern void rcu_scheduler_starting(void);
#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
#include <linux/rcutree.h>
(ptr)->next = NULL; (ptr)->func = NULL; \
} while (0)
+static inline void init_rcu_head_on_stack(struct rcu_head *head)
+{
+}
+
+static inline void destroy_rcu_head_on_stack(struct rcu_head *head)
+{
+}
+
#ifdef CONFIG_DEBUG_LOCK_ALLOC
extern struct lockdep_map rcu_lock_map;
# define rcu_read_release_sched() \
lock_release(&rcu_sched_lock_map, 1, _THIS_IP_)
-static inline int debug_lockdep_rcu_enabled(void)
-{
- return likely(rcu_scheduler_active && debug_locks);
-}
+extern int debug_lockdep_rcu_enabled(void);
/**
* rcu_read_lock_held - might we be in RCU read-side critical section?
*
- * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in
- * an RCU read-side critical section. In absence of CONFIG_PROVE_LOCKING,
+ * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU
+ * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC,
* this assumes we are in an RCU read-side critical section unless it can
* prove otherwise.
*
- * Check rcu_scheduler_active to prevent false positives during boot.
+ * Check debug_lockdep_rcu_enabled() to prevent false positives during boot
+ * and while lockdep is disabled.
*/
static inline int rcu_read_lock_held(void)
{
/**
* rcu_read_lock_sched_held - might we be in RCU-sched read-side critical section?
*
- * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in an
- * RCU-sched read-side critical section. In absence of CONFIG_PROVE_LOCKING,
- * this assumes we are in an RCU-sched read-side critical section unless it
- * can prove otherwise. Note that disabling of preemption (including
- * disabling irqs) counts as an RCU-sched read-side critical section.
+ * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an
+ * RCU-sched read-side critical section. In absence of
+ * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side
+ * critical section unless it can prove otherwise. Note that disabling
+ * of preemption (including disabling irqs) counts as an RCU-sched
+ * read-side critical section.
*
- * Check rcu_scheduler_active to prevent false positives during boot.
+ * Check debug_lockdep_rcu_enabled() to prevent false positives during boot
+ * and while lockdep is disabled.
*/
#ifdef CONFIG_PREEMPT
static inline int rcu_read_lock_sched_held(void)
#ifdef CONFIG_PREEMPT
static inline int rcu_read_lock_sched_held(void)
{
- return !rcu_scheduler_active || preempt_count() != 0 || irqs_disabled();
+ return preempt_count() != 0 || irqs_disabled();
}
#else /* #ifdef CONFIG_PREEMPT */
static inline int rcu_read_lock_sched_held(void)
#ifdef CONFIG_PROVE_RCU
+extern int rcu_my_thread_group_empty(void);
+
+#define __do_rcu_dereference_check(c) \
+ do { \
+ static bool __warned; \
+ if (debug_lockdep_rcu_enabled() && !__warned && !(c)) { \
+ __warned = true; \
+ lockdep_rcu_dereference(__FILE__, __LINE__); \
+ } \
+ } while (0)
+
/**
* rcu_dereference_check - rcu_dereference with debug checking
+ * @p: The pointer to read, prior to dereferencing
+ * @c: The conditions under which the dereference will take place
+ *
+ * Do an rcu_dereference(), but check that the conditions under which the
+ * dereference will take place are correct. Typically the conditions indicate
+ * the various locking conditions that should be held at that point. The check
+ * should return true if the conditions are satisfied.
+ *
+ * For example:
+ *
+ * bar = rcu_dereference_check(foo->bar, rcu_read_lock_held() ||
+ * lockdep_is_held(&foo->lock));
*
- * Do an rcu_dereference(), but check that the context is correct.
- * For example, rcu_dereference_check(gp, rcu_read_lock_held()) to
- * ensure that the rcu_dereference_check() executes within an RCU
- * read-side critical section. It is also possible to check for
- * locks being held, for example, by using lockdep_is_held().
+ * could be used to indicate to lockdep that foo->bar may only be dereferenced
+ * if either the RCU read lock is held, or that the lock required to replace
+ * the bar struct at foo->bar is held.
+ *
+ * Note that the list of conditions may also include indications of when a lock
+ * need not be held, for example during initialisation or destruction of the
+ * target struct:
+ *
+ * bar = rcu_dereference_check(foo->bar, rcu_read_lock_held() ||
+ * lockdep_is_held(&foo->lock) ||
+ * atomic_read(&foo->usage) == 0);
*/
#define rcu_dereference_check(p, c) \
({ \
- if (debug_lockdep_rcu_enabled() && !(c)) \
- lockdep_rcu_dereference(__FILE__, __LINE__); \
+ __do_rcu_dereference_check(c); \
rcu_dereference_raw(p); \
})
+/**
+ * rcu_dereference_protected - fetch RCU pointer when updates prevented
+ *
+ * Return the value of the specified RCU-protected pointer, but omit
+ * both the smp_read_barrier_depends() and the ACCESS_ONCE(). This
+ * is useful in cases where update-side locks prevent the value of the
+ * pointer from changing. Please note that this primitive does -not-
+ * prevent the compiler from repeating this reference or combining it
+ * with other references, so it should not be used without protection
+ * of appropriate locks.
+ */
+#define rcu_dereference_protected(p, c) \
+ ({ \
+ __do_rcu_dereference_check(c); \
+ (p); \
+ })
+
#else /* #ifdef CONFIG_PROVE_RCU */
#define rcu_dereference_check(p, c) rcu_dereference_raw(p)
+#define rcu_dereference_protected(p, c) (p)
#endif /* #else #ifdef CONFIG_PROVE_RCU */
+/**
+ * rcu_access_pointer - fetch RCU pointer with no dereferencing
+ *
+ * Return the value of the specified RCU-protected pointer, but omit the
+ * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful
+ * when the value of this pointer is accessed, but the pointer is not
+ * dereferenced, for example, when testing an RCU-protected pointer against
+ * NULL. This may also be used in cases where update-side locks prevent
+ * the value of the pointer from changing, but rcu_dereference_protected()
+ * is a lighter-weight primitive for this use case.
+ */
+#define rcu_access_pointer(p) ACCESS_ONCE(p)
+
/**
* rcu_read_lock - mark the beginning of an RCU read-side critical section.
*
git.openpandora.org / pandora-kernel.git / blobdiff