hrtimer: Fix extra wakeups from __remove_hrtimer()
PATCH 1/1 hrtimer: Fix extra wakeups from __remove_hrtimer()
__remove_hrtimer() attempts to reprogram the clockevent device when the timer being removed is the next to expire. However, __remove_hrtimer() reprograms the clockevent *before* removing the timer from the timerqueue and thus when hrtimer_force_reprogram() finds the next timer to expire it finds the timer we're trying to remove.
This is especially noticeable when the system switches to NOHz mode and the system tick is removed. The timer tick is removed from the system but the clockevent is programmed to wakeup in another HZ anyway.
Silence the extra wakeup by removing the timer from the timerqueue before calling hrtimer_force_reprogram() so that we actually program the clockevent for the next timer to expire.
This was broken by 998adc3 "hrtimers: Convert hrtimers to use timerlist infrastructure".
--- kernel/hrtimer.c | 6 ++++-- 1 files changed, 4 insertions(+), 2 deletions(-)
kernel/hrtimer.c +4 -2
@@ -885,10 +885,13 @@ static void __remove_hrtimer(struct hrtimer *timer,struct hrtimer_clock_base *base, unsigned long newstate, int reprogram) { + struct timerqueue_node *next_timer;if (!(timer->state &HRTIMER_STATE_ENQUEUED )) goto out; -if (&timer->node ==timerqueue_getnext (&base->active)) { + next_timer =timerqueue_getnext (&base->active); +timerqueue_del (&base->active, &timer->node); +if (&timer->node == next_timer) {#ifdef CONFIG_HIGH_RES_TIMERS /* Reprogram the clock event device. if enabled */ if (reprogram &&hrtimer_hres_active ()) {
@@ -901,7 +904,6 @@ static void __remove_hrtimer(struct hrtimer *timer, }#endif } -timerqueue_del (&base->active, &timer->node);if (!timerqueue_getnext (&base->active)) base->cpu_base->active_bases &= ~(1 << base->index); out:
Signature · 2 lines
Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
Quoted 11 lines · Jeff Ohlstein
__remove_hrtimer()attempts to reprogram the clockevent device when the timer being removed is the next to expire. However,__remove_hrtimer()reprograms the clockevent *before* removing the timer from the timerqueue and thus whenhrtimer_force_reprogram()finds the next timer to expire it finds the timer we're trying to remove.This is especially noticeable when the system switches to NOHz mode and the system tick is removed. The timer tick is removed from the system but the clockevent is programmed to wakeup in another HZ anyway.
Reduced one needless call of hrtimer_interrupt() indeed.
Quoted 7 lines
Silence the extra wakeup by removing the timer from the timerqueue before calling
hrtimer_force_reprogram()so that we actually program the clockevent for the next timer to expire.This was broken by 998adc3 "hrtimers: Convert hrtimers to use timerlist infrastructure".
The issue also exists before 998adc3.
Apart from that.
Quoted 42 lines
Signed-off-by Jeff Ohlstein <[email protected]>--- kernel/hrtimer.c | 6 ++++-- 1 files changed, 4 insertions(+), 2 deletions(-)kernel/hrtimer.c +4
-2@@ -885,10 +885,13 @@ static void __remove_hrtimer(struct hrtimer *timer,struct hrtimer_clock_base *base, unsigned long newstate, int reprogram) { + struct timerqueue_node *next_timer;if (!(timer->state &HRTIMER_STATE_ENQUEUED )) goto out; -if (&timer->node ==timerqueue_getnext (&base->active)) { + next_timer =timerqueue_getnext (&base->active); +timerqueue_del (&base->active, &timer->node); +if (&timer->node == next_timer) {#ifdef CONFIG_HIGH_RES_TIMERS /* Reprogram the clock event device. if enabled */ if (reprogram &&hrtimer_hres_active ()) {@@ -901,7 +904,6 @@ static void __remove_hrtimer(struct hrtimer *timer, }#endif } -timerqueue_del (&base->active, &timer->node);if (!timerqueue_getnext (&base->active)) base->cpu_base->active_bases &= ~(1 << base->index); out:Signature · 8 lines
Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Commit-ID: 27c9cd7e601632b3794e1c3344d37b86917ffb43 Gitweb: http://git.kernel.org/tip/27c9cd7e601632b3794e1c3344d37b86917ffb43 Author: Jeff Ohlstein <[email protected]> AuthorDate: Fri, 18 Nov 2011 15:47:10 -0800 Committer: Thomas Gleixner <[email protected]> CommitDate: Sat, 19 Nov 2011 12:17:37 +0100
hrtimer: Fix extra wakeups from __remove_hrtimer()
__remove_hrtimer() attempts to reprogram the clockevent device when the timer being removed is the next to expire. However, __remove_hrtimer() reprograms the clockevent *before* removing the timer from the timerqueue and thus when hrtimer_force_reprogram() finds the next timer to expire it finds the timer we're trying to remove.
This is especially noticeable when the system switches to NOHz mode and the system tick is removed. The timer tick is removed from the system but the clockevent is programmed to wakeup in another HZ anyway.
Silence the extra wakeup by removing the timer from the timerqueue before calling hrtimer_force_reprogram() so that we actually program the clockevent for the next timer to expire.
This was broken by 998adc3 "hrtimers: Convert hrtimers to use timerlist infrastructure".
--- kernel/hrtimer.c | 6 ++++-- 1 files changed, 4 insertions(+), 2 deletions(-)
kernel/hrtimer.c +4 -2
@@ -885,10 +885,13 @@ static void __remove_hrtimer(struct hrtimer *timer,struct hrtimer_clock_base *base, unsigned long newstate, int reprogram) { + struct timerqueue_node *next_timer;if (!(timer->state &HRTIMER_STATE_ENQUEUED )) goto out; -if (&timer->node ==timerqueue_getnext (&base->active)) { + next_timer =timerqueue_getnext (&base->active); +timerqueue_del (&base->active, &timer->node); +if (&timer->node == next_timer) {#ifdef CONFIG_HIGH_RES_TIMERS /* Reprogram the clock event device. if enabled */ if (reprogram &&hrtimer_hres_active ()) {
@@ -901,7 +904,6 @@ static void __remove_hrtimer(struct hrtimer *timer, }#endif } -timerqueue_del (&base->active, &timer->node);if (!timerqueue_getnext (&base->active)) base->cpu_base->active_bases &= ~(1 << base->index); out: