From cc5f730b41506d37a5c2826b2e801d0a59853d11 Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@redhat.com>
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 <peterz@infradead.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
---
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);