From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oleg Nesterov Subject: [PATCH v2 4/8] percpu-rwsem: introduce percpu_down_read_trylock() Date: Tue, 11 Aug 2015 19:04:07 +0200 Message-ID: <20150811170407.GA26914@redhat.com> References: <20150811170343.GA26881@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "Paul E. McKenney" , Peter Zijlstra , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: Al Viro , Dave Chinner , Dave Hansen , Jan Kara Return-path: Content-Disposition: inline In-Reply-To: <20150811170343.GA26881@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Add percpu_down_read_trylock(), it will have the user soon. Signed-off-by: Oleg Nesterov --- include/linux/percpu-rwsem.h | 1 + kernel/locking/percpu-rwsem.c | 13 +++++++++++++ 2 files changed, 14 insertions(+), 0 deletions(-) diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h index 3e58226..3ebf982 100644 --- a/include/linux/percpu-rwsem.h +++ b/include/linux/percpu-rwsem.h @@ -17,6 +17,7 @@ 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 *); diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c index 2c54c64..4bc2127 100644 --- a/kernel/locking/percpu-rwsem.c +++ b/kernel/locking/percpu-rwsem.c @@ -73,6 +73,19 @@ 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_); -- 1.5.5.1