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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-internal.h
parentc34bec5a44e9486597d78e7a686b2f9088a0564c (diff)
downloadlinaro-lsk-fb02fbc14d17837b4b7b02dbb36142c16a7bf208.tar.gz
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-internal.h')
-rw-r--r--kernel/time/tick-internal.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h
index 469248782c2..b1c05bf75ee 100644
--- a/kernel/time/tick-internal.h
+++ b/kernel/time/tick-internal.h
@@ -36,6 +36,7 @@ extern void tick_broadcast_switch_to_oneshot(void);
extern void tick_shutdown_broadcast_oneshot(unsigned int *cpup);
extern int tick_resume_broadcast_oneshot(struct clock_event_device *bc);
extern int tick_broadcast_oneshot_active(void);
+extern void tick_check_oneshot_broadcast(int cpu);
# else /* BROADCAST */
static inline void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
{
@@ -45,6 +46,7 @@ static inline void tick_broadcast_oneshot_control(unsigned long reason) { }
static inline void tick_broadcast_switch_to_oneshot(void) { }
static inline void tick_shutdown_broadcast_oneshot(unsigned int *cpup) { }
static inline int tick_broadcast_oneshot_active(void) { return 0; }
+static inline void tick_check_oneshot_broadcast(int cpu) { }
# endif /* !BROADCAST */
#else /* !ONESHOT */