linux-kernel - [PATCH] softirq: Avoid stack switch from ksoftirqd

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Date:	Wed, 2 Feb 2011 17:10:48 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	LKML <linux-kernel@...r.kernel.org>
cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	David Miller <davem@...emloft.net>,
	Paul Mundt <lethal@...ux-sh.org>
Subject: [PATCH] softirq: Avoid stack switch from ksoftirqd

ksoftirqd() calls do_softirq() which switches stacks on several
architectures. That makes no sense at all. ksoftirqd's stack is
sufficient.

Call __do_softirq() directly.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 kernel/softirq.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Index: linux-2.6-tip/kernel/softirq.c
===================================================================
--- linux-2.6-tip.orig/kernel/softirq.c
+++ linux-2.6-tip/kernel/softirq.c
@@ -738,7 +738,10 @@ static int run_ksoftirqd(void * __bind_c
 			   don't process */
 			if (cpu_is_offline((long)__bind_cpu))
 				goto wait_to_die;
-			do_softirq();
+			local_irq_disable();
+			if (local_softirq_pending())
+				__do_softirq();
+			local_irq_enable();
 			preempt_enable_no_resched();
 			cond_resched();
 			preempt_disable();
--
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