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authorFrederic Weisbecker <fweisbec@gmail.com>2013-02-20 16:15:36 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-03-28 12:12:27 -0700
commit5899ef0b272b58f2927eb3376afaad2b02559180 (patch)
treee74731ea62cd7ba183152d23eef8e39a536f207e
parentcbff2b6d371dbbae19de1dcfd09051683eca02ca (diff)
nohz: Make tick_nohz_irq_exit() irq safe
commit e5ab012c3271990e8457055c25cafddc1ae8aa6b upstream. As it stands, irq_exit() may or may not be called with irqs disabled, depending on __ARCH_IRQ_EXIT_IRQS_DISABLED that the arch can define. It makes tick_nohz_irq_exit() unsafe. For example two interrupts can race in tick_nohz_stop_sched_tick(): the inner most one computes the expiring time on top of the timer list, then it's interrupted right before reprogramming the clock. The new interrupt enqueues a new timer list timer, it reprogram the clock to take it into account and it exits. The CPUs resumes the inner most interrupt and performs the clock reprogramming without considering the new timer list timer. This regression has been introduced by: 280f06774afedf849f0b34248ed6aff57d0f6908 ("nohz: Separate out irq exit and idle loop dyntick logic") Let's fix it right now with the appropriate protections. A saner long term solution will be to remove __ARCH_IRQ_EXIT_IRQS_DISABLED and mandate that irq_exit() is called with interrupts disabled. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Linus Torvalds <torvalds@linuxfoundation.org> Link: http://lkml.kernel.org/r/1361373336-11337-1-git-send-email-fweisbec@gmail.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Lingzhu Xiang <lxiang@redhat.com> Reviewed-by: CAI Qian <caiqian@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--kernel/time/tick-sched.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index e60347797359..01d8e62ac369 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -496,12 +496,17 @@ void tick_nohz_idle_enter(void)
*/
void tick_nohz_irq_exit(void)
{
+ unsigned long flags;
struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
if (!ts->inidle)
return;
+ local_irq_save(flags);
+
tick_nohz_stop_sched_tick(ts);
+
+ local_irq_restore(flags);
}
/**