percpu_down_write() does down_write() to exclude both the readers and
other writers. We can rely on rcu_sync_enter() in exclusive mode and
take ->rw_sem right before wait_event().
Signed-off-by: Oleg Nesterov <o...@redhat.com>
---
kernel/locking/percpu-rwsem.c | 3 +--
1 files changed, 1 insertions(+), 2 deletions(-)
diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
index 014d2f4..609c13b 100644
--- a/kernel/locking/percpu-rwsem.c
+++ b/kernel/locking/percpu-rwsem.c
@@ -139,8 +139,6 @@ static bool readers_active_check(struct percpu_rw_semaphore
*sem)
void percpu_down_write(struct percpu_rw_semaphore *sem)
{
- down_write(&sem->rw_sem);
-
/* Notify readers to take the slow path. */
rcu_sync_enter(&sem->rss);
@@ -158,6 +156,7 @@ void percpu_down_write(struct percpu_rw_semaphore *sem)
* therefore will wait for them.
*/
+ down_write(&sem->rw_sem);
/* Wait for all now active readers to complete. */
wait_event(sem->writer, readers_active_check(sem));
}
--
1.5.5.1
--
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