From: Ingo Molnar <mingo@elte.hu>
Date: Fri, 7 Dec 2007 18:02:47 +0000 (+0100)
Subject: sched: enable early use of sched_clock()
X-Git-Tag: v2.6.24-rc5~50^2
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=8ced5f69e4bc09adcc6442e090e2e64c197246cf;p=linux-2.6-omap-h63xx.git

sched: enable early use of sched_clock()

some platforms have sched_clock() implementations that cannot be called
very early during wakeup. If it's called it might hang or crash in hard
to debug ways. So only call update_rq_clock() [which calls sched_clock()]
if sched_init() has already been called. (rq->idle is NULL before the
scheduler is initialized.)

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

diff --git a/kernel/sched.c b/kernel/sched.c
index 67d9d1799d8..c6e551de795 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -488,7 +488,12 @@ unsigned long long cpu_clock(int cpu)
 
 	local_irq_save(flags);
 	rq = cpu_rq(cpu);
-	update_rq_clock(rq);
+	/*
+	 * Only call sched_clock() if the scheduler has already been
+	 * initialized (some code might call cpu_clock() very early):
+	 */
+	if (rq->idle)
+		update_rq_clock(rq);
 	now = rq->clock;
 	local_irq_restore(flags);