Commit 92896bd9 authored Mar 24, 2008 by Linus Torvalds

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>

parent d2532dd2

kernel/time/timekeeping.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -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) { }