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authorIngo Molnar <mingo@elte.hu>2008-05-12 15:43:53 +0200
committerIngo Molnar <mingo@elte.hu>2008-05-30 14:15:02 +0200
commit02ff375590ac4140d88afc76505df1ad45c6af59 (patch)
tree6c24cfb6d0e652f691325dc63afab1373b808442
parent1c4cd6dd1d0fd3057bb6b8c87460049497889d1b (diff)
softlockup: fix false positives on nohz if CPU is 100% idle for more than 60 seconds
Fix (probably theoretical only) rq->clock update bug: in tick_nohz_update_jiffies() [which is called on all irq entry on all cpus where the irq entry hits an idle cpu] we call touch_softlockup_watchdog() before we update jiffies. That works fine most of the time when idle timeouts are within 60 seconds. But when an idle timeout is beyond 60 seconds, jiffies is updated with a jump of more than 60 seconds, which causes a jump in cpu-clock of more than 60 seconds, triggering a false positive. Reported-by: David Miller <davem@davemloft.net> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--kernel/time/tick-sched.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index b854a895591e..28abad66fc8e 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -133,8 +133,6 @@ void tick_nohz_update_jiffies(void)
if (!ts->tick_stopped)
return;
- touch_softlockup_watchdog();
-
cpu_clear(cpu, nohz_cpu_mask);
now = ktime_get();
ts->idle_waketime = now;
@@ -142,6 +140,8 @@ void tick_nohz_update_jiffies(void)
local_irq_save(flags);
tick_do_update_jiffies64(now);
local_irq_restore(flags);
+
+ touch_softlockup_watchdog();
}
void tick_nohz_stop_idle(int cpu)