From fb02fbc14d17837b4b7b02dbb36142c16a7bf208 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Fri, 17 Oct 2008 10:01:23 +0200 Subject: NOHZ: restart tick device from irq_enter() We did not restart the tick device from irq_enter() to avoid double reprogramming and extra events in the return immediate to idle case. But long lasting softirqs can lead to a situation where jiffies become stale: idle() tick stopped (reprogrammed to next pending timer) halt() interrupt jiffies updated from irq_enter() interrupt handler softirq function 1 runs 20ms softirq function 2 arms a 10ms timer with a stale jiffies value jiffies updated from irq_exit() timer wheel has now an already expired timer (the one added in function 2) timer fires and timer softirq runs This was discovered when debugging a timer problem which happend only when the ath5k driver is active. The debugging proved that there is a softirq function running for more than 20ms, which is a bug by itself. To solve this we restart the tick timer right from irq_enter(), but do not go through the other functions which are necessary to return from idle when need_resched() is set. Reported-by: Elias Oltmanns Signed-off-by: Thomas Gleixner Tested-by: Elias Oltmanns --- kernel/time/tick-broadcast.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'kernel/time/tick-broadcast.c') diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c index cb01cd8f919b..f98a1b7b16e9 100644 --- a/kernel/time/tick-broadcast.c +++ b/kernel/time/tick-broadcast.c @@ -383,6 +383,19 @@ int tick_resume_broadcast_oneshot(struct clock_event_device *bc) return 0; } +/* + * Called from irq_enter() when idle was interrupted to reenable the + * per cpu device. + */ +void tick_check_oneshot_broadcast(int cpu) +{ + if (cpu_isset(cpu, tick_broadcast_oneshot_mask)) { + struct tick_device *td = &per_cpu(tick_cpu_device, cpu); + + clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_ONESHOT); + } +} + /* * Handle oneshot mode broadcasting */ -- cgit v1.2.3