path: root/kernel
diff options
authorThomas Gleixner <tglx@linutronix.de>2008-10-21 20:17:35 +0200
committerThomas Gleixner <tglx@linutronix.de>2008-10-21 20:53:24 +0200
commitc4bd822e7b12a9008241d76db45b665f2fef180c (patch)
treebd4b7b4e2e7db065c971eb264196f02e0b01ecff /kernel
parent2515ddc6db8eb49a79f0fe5e67ff09ac7c81eab4 (diff)
NOHZ: fix thinko in the timer restart code path
commit fb02fbc14d17837b4b7b02dbb36142c16a7bf208 (NOHZ: restart tick device from irq_enter()) solves the problem of stale jiffies when long running softirqs happen in a long idle sleep period, but it has a major thinko in it: When the interrupt which came in _is_ the timer interrupt which should expire ts->sched_timer then we cancel and rearm the timer _before_ it gets expired in hrtimer_interrupt() to the next period. That means the call back function is not called. This game can go on for ever :( Prevent this by making sure to only rearm the timer when the expiry time is more than one tick_period away. Otherwise keep it running as it is either already expired or will expiry at the right point to update jiffies. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Venkatesch Pallipadi <venkatesh.pallipadi@intel.com>
Diffstat (limited to 'kernel')
1 files changed, 11 insertions, 1 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 0581c11fe6c..727c1ae0517 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -567,11 +567,21 @@ static void tick_nohz_switch_to_nohz(void)
static void tick_nohz_kick_tick(int cpu)
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+ ktime_t delta, now;
if (!ts->tick_stopped)
- tick_nohz_restart(ts, ktime_get());
+ /*
+ * Do not touch the tick device, when the next expiry is either
+ * already reached or less/equal than the tick period.
+ */
+ now = ktime_get();
+ delta = ktime_sub(ts->sched_timer.expires, now);
+ if (delta.tv64 <= tick_period.tv64)
+ return;
+ tick_nohz_restart(ts, now);