hrtimer: unlock hrtimer_wakeup

hrtimer_wakeup creates a

  base->lock
    rq->lock

lock dependancy. Avoid this by switching to HRTIMER_CB_IRQSAFE_NO_SOFTIRQ
which doesn't hold base->lock.

This fully untangles hrtimer locks from the scheduler locks, and allows
hrtimer usage in the scheduler proper.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 3 insertions, 1 deletions

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 061ae28a36a0..bd5d6b5060bc 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1293,7 +1293,7 @@ void hrtimer_init_sleeper(struct hrtimer_sleeper *sl, struct task_struct *task)
         sl->timer.function = hrtimer_wakeup;
         sl->task = task;
 #ifdef CONFIG_HIGH_RES_TIMERS
-        sl->timer.cb_mode = HRTIMER_CB_IRQSAFE_NO_RESTART;
+        sl->timer.cb_mode = HRTIMER_CB_IRQSAFE_NO_SOFTIRQ;
 #endif
 }
 
@@ -1304,6 +1304,8 @@ static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mod
         do {
                 set_current_state(TASK_INTERRUPTIBLE);
                 hrtimer_start(&t->timer, t->timer.expires, mode);
+                if (!hrtimer_active(&t->timer))
+                        t->task = NULL;
 
                 if (likely(t->task))
                         schedule();