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| author | Leonid Shatz <leonid.shatz@ravellosystems.com> | 2013-02-04 14:33:37 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2013-02-05 11:52:41 +0100 |
| commit | b22affe0aef429d657bc6505aacb1c569340ddd2 (patch) | |
| tree | 6cdb5271ab0f4d02ccca8130fb0c0de8f61fe37a /kernel | |
| parent | 90889a635a9b5488624bccce3ff6b2eec68c007b (diff) | |
| download | linux-b22affe0aef429d657bc6505aacb1c569340ddd2.tar.gz linux-b22affe0aef429d657bc6505aacb1c569340ddd2.tar.bz2 linux-b22affe0aef429d657bc6505aacb1c569340ddd2.zip | |
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>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/hrtimer.c | 36 |
1 files changed, 18 insertions, 18 deletions
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index 6db7a5ed52b5..cdd5607c0ceb 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -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); |