From cc5f730b41506d37a5c2826b2e801d0a59853d11 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Fri, 21 Aug 2015 19:43:03 +0200 Subject: [PATCH] locking/percpu-rwsem: Clean up the lockdep annotations in percpu_down_read() Based on Peter Zijlstra's earlier patch. Change percpu_down_read() to use __down_read(), this way we can do rwsem_acquire_read() unconditionally at the start to make this code more symmetric and clean. Originally-From: Peter Zijlstra Signed-off-by: Oleg Nesterov Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- kernel/locking/percpu-rwsem.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c index 02a726dd9adc..f231e0bb311c 100644 --- a/kernel/locking/percpu-rwsem.c +++ b/kernel/locking/percpu-rwsem.c @@ -70,14 +70,14 @@ static bool update_fast_ctr(struct percpu_rw_semaphore *brw, unsigned int val) void percpu_down_read(struct percpu_rw_semaphore *brw) { might_sleep(); - if (likely(update_fast_ctr(brw, +1))) { - rwsem_acquire_read(&brw->rw_sem.dep_map, 0, 0, _RET_IP_); - return; - } + rwsem_acquire_read(&brw->rw_sem.dep_map, 0, 0, _RET_IP_); - down_read(&brw->rw_sem); + if (likely(update_fast_ctr(brw, +1))) + return; + + /* Avoid rwsem_acquire_read() and rwsem_release() */ + __down_read(&brw->rw_sem); atomic_inc(&brw->slow_read_ctr); - /* avoid up_read()->rwsem_release() */ __up_read(&brw->rw_sem); } EXPORT_SYMBOL_GPL(percpu_down_read);