Commit 31784cff authored by Eric W. Biederman's avatar Eric W. Biederman Committed by Peter Zijlstra
Browse files

rwsem: Implement down_read_interruptible 



In preparation for converting exec_update_mutex to a rwsem so that
multiple readers can execute in parallel and not deadlock, add
down_read_interruptible.  This is needed for perf_event_open to be
converted (with no semantic changes) from working on a mutex to
wroking on a rwsem.

Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/87k0tybqfy.fsf@x220.int.ebiederm.org
parent 0f9368b5

include/linux/rwsem.h

+1 −0
Original line number Diff line number Diff line
@@ -123,6 +123,7 @@ static inline int rwsem_is_contended(struct rw_semaphore *sem) 
 * lock for reading

 */

extern void down_read(struct rw_semaphore *sem);

extern int __must_check down_read_interruptible(struct rw_semaphore *sem);

extern int __must_check down_read_killable(struct rw_semaphore *sem);



/*

kernel/locking/rwsem.c

+26 −0
Original line number Diff line number Diff line
@@ -1345,6 +1345,18 @@ static inline void __down_read(struct rw_semaphore *sem) 
	}

}



static inline int __down_read_interruptible(struct rw_semaphore *sem)

{

	if (!rwsem_read_trylock(sem)) {

		if (IS_ERR(rwsem_down_read_slowpath(sem, TASK_INTERRUPTIBLE)))

			return -EINTR;

		DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem);

	} else {

		rwsem_set_reader_owned(sem);

	}

	return 0;

}



static inline int __down_read_killable(struct rw_semaphore *sem)

{

	if (!rwsem_read_trylock(sem)) {
@@ -1495,6 +1507,20 @@ void __sched down_read(struct rw_semaphore *sem) 
}

EXPORT_SYMBOL(down_read);



int __sched down_read_interruptible(struct rw_semaphore *sem)

{

	might_sleep();

	rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);



	if (LOCK_CONTENDED_RETURN(sem, __down_read_trylock, __down_read_interruptible)) {

		rwsem_release(&sem->dep_map, _RET_IP_);

		return -EINTR;

	}



	return 0;

}

EXPORT_SYMBOL(down_read_interruptible);



int __sched down_read_killable(struct rw_semaphore *sem)

{

	might_sleep();