linux-kernel - [PATCH 1/4] workqueue: allow more off-queue flag space

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Message-ID: <20130219201941.GU17414@htj.dyndns.org>
Date:	Tue, 19 Feb 2013 12:19:41 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH 1/4] workqueue: allow more off-queue flag space

>From 4acd43237af61d55ac128bbaf46ca092d560809c Mon Sep 17 00:00:00 2001
From: Lai Jiangshan <laijs@...fujitsu.com>
Date: Tue, 19 Feb 2013 12:17:01 -0800

When a work item is off-queue, its work->data contains WORK_STRUCT_*
and WORK_OFFQ_* flags.  As WORK_OFFQ_* flags are used only while a
work item is off-queue, it can occupy bits of work->data which aren't
used while off-queue.  WORK_OFFQ_* currently only use bits used by
on-queue CWQ pointer.  As color bits aren't used while off-queue,
there's no reason to not use them.

Lower WORK_OFFQ_FLAG_BASE from WORK_STRUCT_FLAG_BITS to
WORK_STRUCT_COLOR_SHIFT thus giving 4 more bits to off-queue flag
space which is also used to record worker_pool ID while off-queue.

This doesn't introduce any visible behavior difference.

tj: Rewrote the description.

Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
Signed-off-by: Tejun Heo <tj@...nel.org>
---
Applied to wq/for-3.10-tmp.  Note that I'm gonna reabse the branch
once 3.9-rc1 is out.

Thanks.

 include/linux/workqueue.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 8afab27..5bd030f 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -68,7 +68,7 @@ enum {
 				  WORK_STRUCT_COLOR_BITS,

 	/* data contains off-queue information when !WORK_STRUCT_PWQ */
-	WORK_OFFQ_FLAG_BASE	= WORK_STRUCT_FLAG_BITS,
+	WORK_OFFQ_FLAG_BASE	= WORK_STRUCT_COLOR_SHIFT,

 	WORK_OFFQ_CANCELING	= (1 << WORK_OFFQ_FLAG_BASE),

-- 
1.8.1

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