summaryrefslogtreecommitdiffstats
path: root/arch/arm
diff options
context:
space:
mode:
authorThomas Gleixner <tglx@linutronix.de>2012-05-26 00:08:59 +0200
committerThomas Gleixner <tglx@linutronix.de>2012-06-06 13:49:02 +0200
commite40468a54882ef7411fb178dbf2e465ec2349af7 (patch)
tree5c7859bb5b325752694b3fd0bccbce7b4997dab2 /arch/arm
parenttimers: Add accounting of non deferrable timers (diff)
downloadlinux-e40468a54882ef7411fb178dbf2e465ec2349af7.tar.xz
linux-e40468a54882ef7411fb178dbf2e465ec2349af7.zip
timers: Improve get_next_timer_interrupt()
Gilad reported at http://lkml.kernel.org/r/1336056962-10465-2-git-send-email-gilad@benyossef.com "Current timer code fails to correctly return a value meaning that there is no future timer event, with the result that the timer keeps getting re-armed in HZ one shot mode even when we could turn it off, generating unneeded interrupts. What is happening is that when __next_timer_interrupt() wishes to return a value that signifies "there is no future timer event", it returns (base->timer_jiffies + NEXT_TIMER_MAX_DELTA). However, the code in tick_nohz_stop_sched_tick(), which called __next_timer_interrupt() via get_next_timer_interrupt(), compares the return value to (last_jiffies + NEXT_TIMER_MAX_DELTA) to see if the timer needs to be re-armed. base->timer_jiffies != last_jiffies and so tick_nohz_stop_sched_tick() interperts the return value as indication that there is a distant future event 12 days from now and programs the timer to fire next after KTIME_MAX nsecs instead of avoiding to arm it. This ends up causing a needless interrupt once every KTIME_MAX nsecs." Fix this by using the new active timer accounting. This avoids scans when no active timer is enqueued completely, so we don't have to rely on base->timer_next and base->timer_jiffies anymore. Reported-by: Gilad Ben-Yossef <gilad@benyossef.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Link: http://lkml.kernel.org/r/20120525214819.317535385@linutronix.de
Diffstat (limited to 'arch/arm')
0 files changed, 0 insertions, 0 deletions