linux-kernel - [PATCH 06/10] rwsem: smaller wrappers around rwsem_down_failed

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Date:	Fri, 14 May 2010 05:39:38 -0700
From:	Michel Lespinasse <walken@...gle.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Howells <dhowells@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Waychison <mikew@...gle.com>,
	Suleiman Souhlal <suleiman@...gle.com>,
	Ying Han <yinghan@...gle.com>,
	Michel Lespinasse <walken@...gle.com>
Subject: [PATCH 06/10] rwsem: smaller wrappers around rwsem_down_failed_common

More code can be pushed from rwsem_down_read_failed and
rwsem_down_write_failed into rwsem_down_failed_common.

Following change adding down_read_unfair infrastructure support also
enjoys having flags available in a register rather than having to
fish it out in the struct rwsem_waiter...

Signed-off-by: Michel Lespinasse <walken@...gle.com>
---
 lib/rwsem.c |   25 ++++++++++---------------
 1 files changed, 10 insertions(+), 15 deletions(-)

diff --git a/lib/rwsem.c b/lib/rwsem.c
index 6e1200e..2dd1a1b 100644
--- a/lib/rwsem.c
+++ b/lib/rwsem.c
@@ -170,8 +170,9 @@ __rwsem_do_wake(struct rw_semaphore *sem, int wake_type)
  */
 static struct rw_semaphore __sched *
 rwsem_down_failed_common(struct rw_semaphore *sem,
-			struct rwsem_waiter *waiter, signed long adjustment)
+			 unsigned int flags, signed long adjustment)
 {
+	struct rwsem_waiter waiter;
 	struct task_struct *tsk = current;
 	signed long count;
 
@@ -179,12 +180,13 @@ rwsem_down_failed_common(struct rw_semaphore *sem,
 
 	/* set up my own style of waitqueue */
 	spin_lock_irq(&sem->wait_lock);
-	waiter->task = tsk;
+	waiter.task = tsk;
+	waiter.flags = flags;
 	get_task_struct(tsk);
 
 	if (list_empty(&sem->wait_list))
 		adjustment += RWSEM_WAITING_BIAS;
-	list_add_tail(&waiter->list, &sem->wait_list);
+	list_add_tail(&waiter.list, &sem->wait_list);
 
 	/* we're now waiting on the lock, but no longer actively locking */
 	count = rwsem_atomic_update(adjustment, sem);
@@ -205,7 +207,7 @@ rwsem_down_failed_common(struct rw_semaphore *sem,
 
 	/* wait to be given the lock */
 	for (;;) {
-		if (!waiter->task)
+		if (!waiter.task)
 			break;
 		schedule();
 		set_task_state(tsk, TASK_UNINTERRUPTIBLE);
@@ -222,11 +224,8 @@ rwsem_down_failed_common(struct rw_semaphore *sem,
 asmregparm struct rw_semaphore __sched *
 rwsem_down_read_failed(struct rw_semaphore *sem)
 {
-	struct rwsem_waiter waiter;
-
-	waiter.flags = RWSEM_WAITING_FOR_READ;
-	rwsem_down_failed_common(sem, &waiter, -RWSEM_ACTIVE_READ_BIAS);
-	return sem;
+	return rwsem_down_failed_common(sem, RWSEM_WAITING_FOR_READ,
+					-RWSEM_ACTIVE_READ_BIAS);
 }
 
 /*
@@ -235,12 +234,8 @@ rwsem_down_read_failed(struct rw_semaphore *sem)
 asmregparm struct rw_semaphore __sched *
 rwsem_down_write_failed(struct rw_semaphore *sem)
 {
-	struct rwsem_waiter waiter;
-
-	waiter.flags = RWSEM_WAITING_FOR_WRITE;
-	rwsem_down_failed_common(sem, &waiter, -RWSEM_ACTIVE_WRITE_BIAS);
-
-	return sem;
+	return rwsem_down_failed_common(sem, RWSEM_WAITING_FOR_WRITE,
+					-RWSEM_ACTIVE_WRITE_BIAS);
 }
 
 /*
-- 
1.7.0.1

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