linux-kernel - [RFC PATCH 2/4] linsched: add check on invoke tick_nohz_irq_exit() in irq

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Message-ID: <50442ACE.9070807@linux.vnet.ibm.com>
Date:	Mon, 03 Sep 2012 11:58:06 +0800
From:	Michael Wang <wangyun@...ux.vnet.ibm.com>
To:	LKML <linux-kernel@...r.kernel.org>
CC:	Paul Turner <pjt@...gle.com>,
	Dhaval Giani <dhaval.giani@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: [RFC PATCH 2/4] linsched: add check on invoke tick_nohz_irq_exit()
 in irq_exit()

From: Michael Wang <wangyun@...ux.vnet.ibm.com>

tick_nohz_irq_exit() will make sure the tick timer reprogram correctly
after cpu enter idle.

With out this check, after the interrupt, tick timer will be enabled
even cpu is still in idle, this will cause inaccuracy.

Signed-off-by: Michael Wang <wangyun@...ux.vnet.ibm.com>
---
 arch/linsched/kernel/irq.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/arch/linsched/kernel/irq.c b/arch/linsched/kernel/irq.c
index 3000d47..5f88af4 100644
--- a/arch/linsched/kernel/irq.c
+++ b/arch/linsched/kernel/irq.c
@@ -2,6 +2,7 @@
 #include <asm/hardirq.h>
 #include <linux/sched.h>
 #include <linux/irq_work.h>
+#include <linux/tick.h>

 unsigned long linsched_irq_flags = ARCH_IRQ_ENABLED;

@@ -87,6 +88,9 @@ void irq_exit(void)
        sub_preempt_count(IRQ_EXIT_OFFSET);
        if (!in_interrupt() && local_softirq_pending())
                do_softirq();
+
+       if (idle_cpu(smp_processor_id()) && !in_interrupt() && !need_resched())
+               tick_nohz_irq_exit();
 }

 void local_bh_enable_ip(unsigned long ip)
--  
1.7.1

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