linux-kernel - [PATCH] kernel/softirq.c: delete 'while' looping to improve a little performance and beautify code

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Date:	Sun, 09 Jun 2013 20:30:19 +0800
From:	Chen Gang <gang.chen@...anux.com>
To:	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Sedat Dilek <sedat.dilek@...il.com>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] kernel/softirq.c: delete 'while' looping to improve a little
 performance and beautify code


After finish the internal 'while', need not test TASKLET_STATE_SCHED
again, so looping back to outside 'while' is only for set_bit().

When use 'if' and set_bit() instead of 'while', it will save at least
one running conditional instruction, and also will be clearer for readers
(although the binary size will be a little bigger).

The related patch is "1da177e Linux-2.6.12-rc2"


Signed-off-by: Chen Gang <gang.chen@...anux.com>
---
 kernel/softirq.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/kernel/softirq.c b/kernel/softirq.c
index a5f8836..52da25f 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -540,10 +540,11 @@ void tasklet_kill(struct tasklet_struct *t)
 	if (in_interrupt())
 		printk("Attempt to kill tasklet from interrupt\n");
 
-	while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) {
+	if (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) {
 		do {
 			yield();
 		} while (test_bit(TASKLET_STATE_SCHED, &t->state));
+		set_bit(TASKLET_STATE_SCHED, &t->state);
 	}
 	tasklet_unlock_wait(t);
 	clear_bit(TASKLET_STATE_SCHED, &t->state);
-- 
1.7.7.6
--
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