linux-kernel - [PATCH 2/3] locking/percpu-rwsem: Replace bulky wait-queues with swait

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Date:   Fri, 18 Nov 2016 10:54:36 -0800
From:   Davidlohr Bueso <dave@...olabs.net>
To:     mingo@...nel.org, peterz@...radead.org, oleg@...hat.com
Cc:     john.stultz@...aro.org, dimitrysh@...gle.com,
        linux-kernel@...r.kernel.org, dave@...olabs.net,
        Davidlohr Bueso <dbueso@...e.de>
Subject: [PATCH 2/3] locking/percpu-rwsem: Replace bulky wait-queues with swait

In the case of the percpu-rwsem, they don't need any of the
fancy/bulky features, such as custom callbacks or fine grained
wakeups.

Users that can convert to simple wait-queues are encouraged to
do so for the various rt and (indirect) performance benefits.

Signed-off-by: Davidlohr Bueso <dbueso@...e.de>
---
 include/linux/percpu-rwsem.h  | 6 +++---
 kernel/locking/percpu-rwsem.c | 8 ++++----
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h
index 5b2e6159b744..82d54a4b9988 100644
--- a/include/linux/percpu-rwsem.h
+++ b/include/linux/percpu-rwsem.h
@@ -4,7 +4,7 @@
 #include <linux/atomic.h>
 #include <linux/rwsem.h>
 #include <linux/percpu.h>
-#include <linux/wait.h>
+#include <linux/swait.h>
 #include <linux/rcu_sync.h>
 #include <linux/lockdep.h>
 
@@ -12,7 +12,7 @@ struct percpu_rw_semaphore {
 	struct rcu_sync		rss;
 	unsigned int __percpu	*read_count;
 	struct rw_semaphore	rw_sem;
-	wait_queue_head_t	writer;
+	struct swait_queue_head	writer;
 	int			readers_block;
 };
 
@@ -22,7 +22,7 @@ static struct percpu_rw_semaphore name = {				\
 	.rss = __RCU_SYNC_INITIALIZER(name.rss, RCU_SCHED_SYNC),	\
 	.read_count = &__percpu_rwsem_rc_##name,			\
 	.rw_sem = __RWSEM_INITIALIZER(name.rw_sem),			\
-	.writer = __WAIT_QUEUE_HEAD_INITIALIZER(name.writer),		\
+	.writer = __SWAIT_QUEUE_HEAD_INITIALIZER(name.writer),		\
 }
 
 extern int __percpu_down_read(struct percpu_rw_semaphore *, int);
diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
index ce182599cf2e..cb71201855f2 100644
--- a/kernel/locking/percpu-rwsem.c
+++ b/kernel/locking/percpu-rwsem.c
@@ -1,7 +1,7 @@
 #include <linux/atomic.h>
 #include <linux/rwsem.h>
 #include <linux/percpu.h>
-#include <linux/wait.h>
+#include <linux/swait.h>
 #include <linux/lockdep.h>
 #include <linux/percpu-rwsem.h>
 #include <linux/rcupdate.h>
@@ -18,7 +18,7 @@ int __percpu_init_rwsem(struct percpu_rw_semaphore *sem,
 	/* ->rw_sem represents the whole percpu_rw_semaphore for lockdep */
 	rcu_sync_init(&sem->rss, RCU_SCHED_SYNC);
 	__init_rwsem(&sem->rw_sem, name, rwsem_key);
-	init_waitqueue_head(&sem->writer);
+	init_swait_queue_head(&sem->writer);
 	sem->readers_block = 0;
 	return 0;
 }
@@ -103,7 +103,7 @@ void __percpu_up_read(struct percpu_rw_semaphore *sem)
 	__this_cpu_dec(*sem->read_count);
 
 	/* Prod writer to recheck readers_active */
-	wake_up(&sem->writer);
+	swake_up(&sem->writer);
 }
 EXPORT_SYMBOL_GPL(__percpu_up_read);
 
@@ -160,7 +160,7 @@ void percpu_down_write(struct percpu_rw_semaphore *sem)
 	 */
 
 	/* Wait for all now active readers to complete. */
-	wait_event(sem->writer, readers_active_check(sem));
+	swait_event(sem->writer, readers_active_check(sem));
 }
 EXPORT_SYMBOL_GPL(percpu_down_write);
 
-- 
2.6.6