linux-kernel - [PATCH 2/3] workqueues: microoptimize set_wq

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Message-ID: <20100224202035.GA26991@redhat.com>
Date:	Wed, 24 Feb 2010 21:20:35 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Samu Onkalo <samu.p.onkalo@...ia.com>,
	Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] workqueues: microoptimize set_wq_data()

The comment correctly states that the _PENDING bit must be set and
we even have the BUG_ON() check. But this means there is no need to
set WORK_STRUCT_PENDING explicitely and load work_data_bits() twice,
we can rely on WORK_STRUCT_FLAG_MASK which contains _PENDING.

Shaves 32 bytes from workqueue.o.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---

 kernel/workqueue.c |    7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

--- wq/kernel/workqueue.c~2_CLEANUP_SET_DATA	2010-02-24 20:55:53.000000000 +0100
+++ wq/kernel/workqueue.c	2010-02-24 20:58:37.000000000 +0100
@@ -220,12 +220,9 @@ struct cpu_workqueue_struct *wq_per_cpu(
 static inline void set_wq_data(struct work_struct *work,
 				struct cpu_workqueue_struct *cwq)
 {
-	unsigned long new;
-
-	BUG_ON(!work_pending(work));
-
-	new = (unsigned long) cwq | (1UL << WORK_STRUCT_PENDING);
+	unsigned long new = (unsigned long)cwq;
 	new |= WORK_STRUCT_FLAG_MASK & *work_data_bits(work);
+	BUG_ON(!(new & (1UL << WORK_STRUCT_PENDING)));
 	atomic_long_set(&work->data, new);
 }
 

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