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percpu-rwsem: introduce percpu_down_read_trylock()

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Add percpu_down_read_trylock(), it will have the user soon.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
This commit is contained in:
Oleg Nesterov 2015-07-21 17:45:57 +02:00
parent 0e28e01f1e
commit 9287f6925a
2 changed files with 14 additions and 0 deletions
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1
include/linux/percpu-rwsem.h
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@ -16,6 +16,7 @@ struct percpu_rw_semaphore {
};
extern void percpu_down_read(struct percpu_rw_semaphore *);
extern int percpu_down_read_trylock(struct percpu_rw_semaphore *);
extern void percpu_up_read(struct percpu_rw_semaphore *);
extern void percpu_down_write(struct percpu_rw_semaphore *);

13
kernel/locking/percpu-rwsem.c
View file

@ -88,6 +88,19 @@ void percpu_down_read(struct percpu_rw_semaphore *brw)
__up_read(&brw->rw_sem);
}
int percpu_down_read_trylock(struct percpu_rw_semaphore *brw)
{
if (unlikely(!update_fast_ctr(brw, +1))) {
if (!__down_read_trylock(&brw->rw_sem))
return 0;
atomic_inc(&brw->slow_read_ctr);
__up_read(&brw->rw_sem);
}
rwsem_acquire_read(&brw->rw_sem.dep_map, 0, 1, _RET_IP_);
return 1;
}
void percpu_up_read(struct percpu_rw_semaphore *brw)
{
rwsem_release(&brw->rw_sem.dep_map, 1, _RET_IP_);