diff options
Diffstat (limited to 'include/linux/rcupdate.h')
| -rw-r--r-- | include/linux/rcupdate.h | 90 |
1 files changed, 64 insertions, 26 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 3024050..db266bb 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -101,10 +101,7 @@ extern struct lockdep_map rcu_sched_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? @@ -123,22 +120,11 @@ static inline int rcu_read_lock_held(void) return lock_is_held(&rcu_lock_map); } -/** - * rcu_read_lock_bh_held - might we be in RCU-bh read-side critical section? - * - * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in - * an RCU-bh read-side critical section. In absence of CONFIG_PROVE_LOCKING, - * this assumes we are in an RCU-bh read-side critical section unless it can - * prove otherwise. - * - * Check rcu_scheduler_active to prevent false positives during boot. +/* + * rcu_read_lock_bh_held() is defined out of line to avoid #include-file + * hell. */ -static inline int rcu_read_lock_bh_held(void) -{ - if (!debug_lockdep_rcu_enabled()) - return 1; - return lock_is_held(&rcu_bh_lock_map); -} +extern int rcu_read_lock_bh_held(void); /** * rcu_read_lock_sched_held - might we be in RCU-sched read-side critical section? @@ -160,7 +146,7 @@ static inline int rcu_read_lock_sched_held(void) return 1; if (debug_locks) lockdep_opinion = lock_is_held(&rcu_sched_lock_map); - return lockdep_opinion || preempt_count() != 0; + return lockdep_opinion || preempt_count() != 0 || irqs_disabled(); } #else /* #ifdef CONFIG_PREEMPT */ static inline int rcu_read_lock_sched_held(void) @@ -191,7 +177,7 @@ static inline int rcu_read_lock_bh_held(void) #ifdef CONFIG_PREEMPT static inline int rcu_read_lock_sched_held(void) { - return !rcu_scheduler_active || preempt_count() != 0; + return !rcu_scheduler_active || preempt_count() != 0 || irqs_disabled(); } #else /* #ifdef CONFIG_PREEMPT */ static inline int rcu_read_lock_sched_held(void) @@ -204,14 +190,34 @@ static inline int rcu_read_lock_sched_held(void) #ifdef CONFIG_PROVE_RCU +extern int rcu_my_thread_group_empty(void); + /** * 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 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(). + * 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)); + * + * 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) \ ({ \ @@ -220,13 +226,45 @@ static inline int rcu_read_lock_sched_held(void) 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) \ + ({ \ + if (debug_lockdep_rcu_enabled() && !(c)) \ + lockdep_rcu_dereference(__FILE__, __LINE__); \ + (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. * * When synchronize_rcu() is invoked on one CPU while other CPUs |