__DEFINE_PERCPU_RWSEM(name, static)
extern bool __percpu_down_read(struct percpu_rw_semaphore *, bool);
-extern void __percpu_up_read(struct percpu_rw_semaphore *);
static inline void percpu_down_read(struct percpu_rw_semaphore *sem)
{
/*
* Same as in percpu_down_read().
*/
- if (likely(rcu_sync_is_idle(&sem->rss)))
+ if (likely(rcu_sync_is_idle(&sem->rss))) {
__this_cpu_dec(*sem->read_count);
- else
- __percpu_up_read(sem); /* Unconditional memory barrier */
+ } else {
+ /*
+ * slowpath; reader will only ever wake a single blocked
+ * writer.
+ */
+ smp_mb(); /* B matches C */
+ /*
+ * In other words, if they see our decrement (presumably to
+ * aggregate zero, as that is the only time it matters) they
+ * will also see our critical section.
+ */
+ __this_cpu_dec(*sem->read_count);
+ rcuwait_wake_up(&sem->writer);
+ }
preempt_enable();
}
}
EXPORT_SYMBOL_GPL(__percpu_down_read);
-void __percpu_up_read(struct percpu_rw_semaphore *sem)
-{
- smp_mb(); /* B matches C */
- /*
- * In other words, if they see our decrement (presumably to aggregate
- * zero, as that is the only time it matters) they will also see our
- * critical section.
- */
- __this_cpu_dec(*sem->read_count);
-
- /* Prod writer to re-evaluate readers_active_check() */
- rcuwait_wake_up(&sem->writer);
-}
-EXPORT_SYMBOL_GPL(__percpu_up_read);
-
#define per_cpu_sum(var) \
({ \
typeof(var) __sum = 0; \