From: Viresh Kumar viresh.kumar@linaro.org
'active_bases' indicates which clock-base have active timer. The intention of this bit field was to avoid evaluating inactive bases. It was introduced with the introduction of the BOOTTIME and TAI clock bases, but it was never brought into full use.
We want to use it now, but in __remove_hrtimer() the update happens after the calling hrtimer_force_reprogram() which has to evaluate all clock bases for the next expiring timer. So in case the last timer of a clock base got removed we still see the active bit and therefor evaluate the clock base for no value. There are further optimizations possible when active_bases is updated in the right place.
Move the update before the call to hrtimer_force_reprogram()
[ tglx: Massaged changelog ]
Reviewed-by: Preeti U Murthy preeti@linux.vnet.ibm.com Signed-off-by: Viresh Kumar viresh.kumar@linaro.org Cc: linaro-kernel@lists.linaro.org Cc: Peter Zijlstra peterz@infradead.org Link: http://lkml.kernel.org/r/c7c8ebcd9ed88bb09d76059c745a1fafb48314e7.1428039899... Signed-off-by: Thomas Gleixner tglx@linutronix.de --- kernel/time/hrtimer.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
Index: tip/kernel/time/hrtimer.c =================================================================== --- tip.orig/kernel/time/hrtimer.c +++ tip/kernel/time/hrtimer.c @@ -879,6 +879,9 @@ static void __remove_hrtimer(struct hrti
next_timer = timerqueue_getnext(&base->active); timerqueue_del(&base->active, &timer->node); + if (!timerqueue_getnext(&base->active)) + base->cpu_base->active_bases &= ~(1 << base->index); + if (&timer->node == next_timer) { #ifdef CONFIG_HIGH_RES_TIMERS /* Reprogram the clock event device. if enabled */ @@ -892,8 +895,6 @@ static void __remove_hrtimer(struct hrti } #endif } - if (!timerqueue_getnext(&base->active)) - base->cpu_base->active_bases &= ~(1 << base->index); out: timer->state = newstate; }