From 9287f6925ad9d8fb8c6283066b4f77fd87f123a9 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 21 Jul 2015 17:45:57 +0200 Subject: [PATCH] percpu-rwsem: introduce percpu_down_read_trylock() 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(+) diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h index 3e88c9a7d57f..16c30cd33501 100644 --- a/include/linux/percpu-rwsem.h +++ b/include/linux/percpu-rwsem.h @@ -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 *); diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c index 652a8ee8efe9..f32567254867 100644 --- a/kernel/locking/percpu-rwsem.c +++ b/kernel/locking/percpu-rwsem.c @@ -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_); -- 2.20.1