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hrtimer: Prevent hrtimer_enqueue_reprogram race 

hrtimer_enqueue_reprogram contains a race which could result in
timer.base switch during unlock/lock sequence.

hrtimer_enqueue_reprogram is releasing the lock protecting the timer
base for calling raise_softirq_irqsoff() due to a lock ordering issue
versus rq->lock.

If during that time another CPU calls __hrtimer_start_range_ns() on
the same hrtimer, the timer base might switch, before the current CPU
can lock base->lock again and therefor the unlock_timer_base() call
will unlock the wrong lock.

[ tglx: Added comment and massaged changelog ]

Signed-off-by: Leonid Shatz <leonid.shatz@ravellosystems.com>
Signed-off-by: Izik Eidus <izik.eidus@ravellosystems.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1359981217-389-1-git-send-email-izik.eidus@ravellosystems.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Leonid Shatz 2013-02-04 14:33:37 +02:00 committed by Thomas Gleixner
parent 90889a635a
commit b22affe0ae
1 changed files with 18 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
kernel/hrtimer.c
View File

@ -640,21 +640,9 @@ static inline void hrtimer_init_hres(struct hrtimer_cpu_base *base)
* and expiry check is done in the hrtimer_interrupt or in the softirq.
*/
static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
struct hrtimer_clock_base *base,
int wakeup)
struct hrtimer_clock_base *base)
{
if (base->cpu_base->hres_active && hrtimer_reprogram(timer, base)) {
if (wakeup) {
raw_spin_unlock(&base->cpu_base->lock);
raise_softirq_irqoff(HRTIMER_SOFTIRQ);
raw_spin_lock(&base->cpu_base->lock);
} else
__raise_softirq_irqoff(HRTIMER_SOFTIRQ);
return 1;
}
return 0;
return base->cpu_base->hres_active && hrtimer_reprogram(timer, base);
}
static inline ktime_t hrtimer_update_base(struct hrtimer_cpu_base *base)
@ -735,8 +723,7 @@ static inline int hrtimer_switch_to_hres(void) { return 0; }
static inline void
hrtimer_force_reprogram(struct hrtimer_cpu_base *base, int skip_equal) { }
static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
struct hrtimer_clock_base *base,
int wakeup)
struct hrtimer_clock_base *base)
{
return 0;
}
@ -995,8 +982,21 @@ int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
*
* XXX send_remote_softirq() ?
*/
if (leftmost && new_base->cpu_base == &__get_cpu_var(hrtimer_bases))
hrtimer_enqueue_reprogram(timer, new_base, wakeup);
if (leftmost && new_base->cpu_base == &__get_cpu_var(hrtimer_bases)
&& hrtimer_enqueue_reprogram(timer, new_base)) {
if (wakeup) {
/*
* We need to drop cpu_base->lock to avoid a
* lock ordering issue vs. rq->lock.
*/
raw_spin_unlock(&new_base->cpu_base->lock);
raise_softirq_irqoff(HRTIMER_SOFTIRQ);
local_irq_restore(flags);
return ret;
} else {
__raise_softirq_irqoff(HRTIMER_SOFTIRQ);
}
}
unlock_hrtimer_base(timer, &flags);