linux-kernel - [tip:timers/urgent] hrtimer, softirq: Fix hrtimer->softirq trampoline

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Date:	Wed, 3 Feb 2010 17:21:34 GMT
From:	tip-bot for Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	a.p.zijlstra@...llo.nl, ypolyans@...nceton.edu,
	davem@...emloft.net, yjwei@...fujitsu.com, tglx@...utronix.de
Subject: [tip:timers/urgent] hrtimer, softirq: Fix hrtimer->softirq trampoline

Commit-ID:  b9c3032277f756e73f6c673419dc414155e04e46
Gitweb:     http://git.kernel.org/tip/b9c3032277f756e73f6c673419dc414155e04e46
Author:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
AuthorDate: Wed, 3 Feb 2010 18:08:52 +0100
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Wed, 3 Feb 2010 18:17:40 +0100

hrtimer, softirq: Fix hrtimer->softirq trampoline

hrtimers callbacks are always done from hardirq context, either the
jiffy tick interrupt or the hrtimer device interrupt.

[ there is currently one exception that can still call a hrtimer
  callback from softirq, but even in that case this will still
  work correctly. ]

Reported-by: Wei Yongjun <yjwei@...fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Yury Polyanskiy <ypolyans@...nceton.edu>
Tested-by: Wei Yongjun <yjwei@...fujitsu.com>
Acked-by: David S. Miller <davem@...emloft.net>
LKML-Reference: <1265120401.24455.306.camel@...top>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 kernel/softirq.c |   15 +++++----------
 1 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/kernel/softirq.c b/kernel/softirq.c
index a09502e..7c1a67e 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -500,22 +500,17 @@ EXPORT_SYMBOL(tasklet_kill);
  */
 
 /*
- * The trampoline is called when the hrtimer expires. If this is
- * called from the hrtimer interrupt then we schedule the tasklet as
- * the timer callback function expects to run in softirq context. If
- * it's called in softirq context anyway (i.e. high resolution timers
- * disabled) then the hrtimer callback is called right away.
+ * The trampoline is called when the hrtimer expires. It schedules a tasklet
+ * to run __tasklet_hrtimer_trampoline() which in turn will call the intended
+ * hrtimer callback, but from softirq context.
  */
 static enum hrtimer_restart __hrtimer_tasklet_trampoline(struct hrtimer *timer)
 {
 	struct tasklet_hrtimer *ttimer =
 		container_of(timer, struct tasklet_hrtimer, timer);
 
-	if (hrtimer_is_hres_active(timer)) {
-		tasklet_hi_schedule(&ttimer->tasklet);
-		return HRTIMER_NORESTART;
-	}
-	return ttimer->function(timer);
+	tasklet_hi_schedule(&ttimer->tasklet);
+	return HRTIMER_NORESTART;
 }
 
 /*
--
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