From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx3-rdu2.redhat.com ([66.187.233.73]:40856 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751365AbeDDOiC (ORCPT ); Wed, 4 Apr 2018 10:38:02 -0400 From: Waiman Long To: Ingo Molnar , Peter Zijlstra , Thomas Gleixner Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Davidlohr Bueso , "Theodore Y. Ts'o" , Oleg Nesterov , Waiman Long Subject: [PATCH] locking/rwsem: Add up_write_non_owner() for percpu_up_write() Date: Wed, 4 Apr 2018 10:37:26 -0400 Message-Id: <1522852646-2196-1-git-send-email-longman@redhat.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: The commit 8c5db92a705d ("locking/rwsem: Add DEBUG_RWSEMS to look for lock/unlock mismatches") causes a warning in ext4 fstests due to the fact that the freeze and thaw ioctls, by design, are run in different processes. This is not a bug in the commit itself. Rather, we need a up_write() variant that annotates the fact that it can be called from a task different from the one that took the lock. The new API is up_write_non_owner() and the percpu_up_write() function is modified to use it instead of the plain up_write(). Signed-off-by: Waiman Long --- include/linux/rwsem.h | 6 ++++++ kernel/locking/percpu-rwsem.c | 4 +++- kernel/locking/rwsem.c | 13 +++++++++++++ 3 files changed, 22 insertions(+), 1 deletion(-) diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h index 56707d5..0e2a425 100644 --- a/include/linux/rwsem.h +++ b/include/linux/rwsem.h @@ -187,4 +187,10 @@ static inline int rwsem_is_contended(struct rw_semaphore *sem) # define up_read_non_owner(sem) up_read(sem) #endif +#ifdef CONFIG_DEBUG_RWSEMS +extern void up_write_non_owner(struct rw_semaphore *sem); +#else +# define up_write_non_owner(sem) up_write(sem) +#endif + #endif /* _LINUX_RWSEM_H */ diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c index 883cf1b..13decf2 100644 --- a/kernel/locking/percpu-rwsem.c +++ b/kernel/locking/percpu-rwsem.c @@ -179,8 +179,10 @@ void percpu_up_write(struct percpu_rw_semaphore *sem) /* * Release the write lock, this will allow readers back in the game. + * percpu_up_write() may be called from a task different from the one + * taking the lock. */ - up_write(&sem->rw_sem); + up_write_non_owner(&sem->rw_sem); /* * Once this completes (at least one RCU-sched grace period hence) the diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 30465a2..140d5ef 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -222,4 +222,17 @@ void up_read_non_owner(struct rw_semaphore *sem) #endif +#ifdef CONFIG_DEBUG_RWSEMS +/* + * release a write lock from a different task + */ +void up_write_non_owner(struct rw_semaphore *sem) +{ + rwsem_release(&sem->dep_map, 1, _RET_IP_); + DEBUG_RWSEMS_WARN_ON(!sem->owner || (sem->owner == RWSEM_READER_OWNED)); + rwsem_clear_owner(sem); + __up_write(sem); +} +EXPORT_SYMBOL(up_write_non_owner); +#endif -- 1.8.3.1