There appears to be a deadlock in the hrtimer code. Specifically, clock_was_set() calls an IPI with wait=1, from softirq context.
Waiting for IPIs to complete in irq context can lead to a deadlock, because the current code (that was interrupted) might be holding some kind of lock, that another CPU is waiting for with spin_lock_irq or similar. In other words, the current CPU may need to release a resource, before the IPI can be handled by one of the destination CPUs. To my untrained eye, it does not look like this patch introduces a new bug to the timer code, but that is hard to ascertain with the timer code. so I am posting this as an RFC for the timer gods to hurt their brains on :) This bug was introduced by 54cdfdb4 in early 2007 (the original hrtimer code patch). Not-yet-signed-off-by: Rik van Riel <[email protected]> Reported-by: Mateusz Guzik <[email protected]> Cc: Benjamin Herrenschmidt <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Prarit Bhargava <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: Clark Williams <[email protected]> --- kernel/hrtimer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index 0909436..19145ec 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -771,7 +771,7 @@ void clock_was_set(void) { #ifdef CONFIG_HIGH_RES_TIMERS /* Retrigger the CPU local events everywhere */ - on_each_cpu(retrigger_next_event, NULL, 1); + on_each_cpu(retrigger_next_event, NULL, 0); #endif timerfd_clock_was_set(); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
