Subject: softlockup: do the wakeup from a hrtimer
From: Ingo Molnar <[email protected]>
David Miller reported soft lockup false-positives that trigger on NOHZ
due to CPUs idling for more than 10 seconds.
The solution is to drive the wakeup of the watchdog threads not from the
timer tick (which has no guaranteed frequency), but from the watchdog
tasks themselves.
http://bugzilla.kernel.org/show_bug.cgi?id=9409
Reported-by: David Miller <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
---
kernel/softlockup.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
Index: linux/kernel/softlockup.c
===================================================================
--- linux.orig/kernel/softlockup.c
+++ linux/kernel/softlockup.c
@@ -100,10 +100,6 @@ void softlockup_tick(void)
now = get_timestamp(this_cpu);
- /* Wake up the high-prio watchdog task every second: */
- if (now > (touch_timestamp + 1))
- wake_up_process(per_cpu(watchdog_task, this_cpu));
-
/* Warn about unreasonable 10+ seconds delays: */
if (now <= (touch_timestamp + softlockup_thresh))
return;
@@ -141,7 +137,7 @@ static int watchdog(void *__bind_cpu)
while (!kthread_should_stop()) {
set_current_state(TASK_INTERRUPTIBLE);
touch_softlockup_watchdog();
- schedule();
+ msleep(1000);
}
return 0;
-
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