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authorThomas Gleixner <tglx@linutronix.de>2008-10-17 10:01:23 +0200
committerThomas Gleixner <tglx@apollo.(none)>2008-10-17 18:13:38 +0200
commitfb02fbc14d17837b4b7b02dbb36142c16a7bf208 (patch)
tree9df1d069c5612047c38a9f6d6dc801ee0369ae3c /kernel/time/tick-broadcast.c
parentc34bec5a44e9486597d78e7a686b2f9088a0564c (diff)
downloadlinux-fb02fbc14d17837b4b7b02dbb36142c16a7bf208.tar.bz2
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 <eo@nebensachen.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Elias Oltmanns <eo@nebensachen.de>
Diffstat (limited to 'kernel/time/tick-broadcast.c')
-rw-r--r--kernel/time/tick-broadcast.c13
1 files changed, 13 insertions, 0 deletions
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
@@ -384,6 +384,19 @@ int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
}
/*
+ * 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
*/
static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)