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Commit 9287f692 authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

percpu-rwsem: introduce percpu_down_read_trylock() 



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

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
parent 0e28e01f

include/linux/percpu-rwsem.h

+1 −0
Original line number Diff line number Diff line
@@ -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 *);

kernel/locking/percpu-rwsem.c

+13 −0
Original line number Diff line number Diff line
@@ -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_);