From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Mon, 24 Mar 2008 18:07:15 +0000 (-0700)
Subject: Don't 'printk()' while holding xtime lock for writing
X-Git-Tag: v2.6.25-rc7~28
X-Git-Url: http://git.samba.org/samba.git/?p=sfrench%2Fcifs-2.6.git;a=commitdiff_plain;h=92896bd9fd75b1c993b92874d339a8088bb75560;ds=sidebyside

Don't 'printk()' while holding xtime lock for writing

The printk() can deadlock because it can wake up klogd(), and
task enqueueing will try to read the time in order to set a hrtimer.

Reported-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Debugged-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 671af612b768..a3fa587c350c 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -191,8 +191,12 @@ static void change_clocksource(void)
 
 	tick_clock_notify();
 
+	/*
+	 * We're holding xtime lock and waking up klogd would deadlock
+	 * us on enqueue.  So no printing!
 	printk(KERN_INFO "Time: %s clocksource has been installed.\n",
 	       clock->name);
+	 */
 }
 #else
 static inline void change_clocksource(void) { }