From: Ingo Molnar <mingo@elte.hu>
Date: Thu, 26 Jul 2007 11:40:43 +0000 (+0200)
Subject: [PATCH] sched: make cpu_clock() not use the rq clock
X-Git-Tag: v2.6.23-rc2~191^2~4
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2cd4d0ea19713304963dbb2de5073700bfe253f5;p=linux-2.6

[PATCH] sched: make cpu_clock() not use the rq clock

it is enough to disable interrupts to get the precise rq-clock
of the local CPU.

this also solves an NMI watchdog regression: the NMI watchdog
calls touch_softlockup_watchdog(), which might deadlock on
rq->lock if the NMI hits an rq-locked critical section.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

diff --git a/kernel/sched.c b/kernel/sched.c
index cc6c1192c4..3eed860cf2 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -383,13 +383,12 @@ static inline unsigned long long rq_clock(struct rq *rq)
  */
 unsigned long long cpu_clock(int cpu)
 {
-	struct rq *rq = cpu_rq(cpu);
 	unsigned long long now;
 	unsigned long flags;
 
-	spin_lock_irqsave(&rq->lock, flags);
-	now = rq_clock(rq);
-	spin_unlock_irqrestore(&rq->lock, flags);
+	local_irq_save(flags);
+	now = rq_clock(cpu_rq(cpu));
+	local_irq_restore(flags);
 
 	return now;
 }