Linus,

please pull hrtimer fixes from:

ssh://master.kernel.org/pub/scm/linux/kernel/git/tglx/linux-2.6-hrt.git master

Fix for a potential deadlock which was introduced with the scheduler
hrtimer changes in .25.

Thanks,
tglx

---
Thomas Gleixner (1):
hrtimer: raise softirq unlocked to avoid circular lock dependency

kernel/hrtimer.c | 19 +++++++++++++++++--
1 files changed, 17 insertions(+), 2 deletions(-)
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index e379ef0..dea4c91 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -590,7 +590,6 @@ static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
list_add_tail(&timer->cb_entry,
&base->cpu_base->cb_pending);
timer->state = HRTIMER_STATE_PENDING;
- raise_softirq(HRTIMER_SOFTIRQ);
return 1;
default:
BUG();
@@ -633,6 +632,11 @@ static int hrtimer_switch_to_hres(void)
return 1;
}

+static inline void hrtimer_raise_softirq(void)
+{
+ raise_softirq(HRTIMER_SOFTIRQ);
+}
+
#else

static inline int hrtimer_hres_active(void) { return 0; }
@@ -651,6 +655,7 @@ static inline int hrtimer_reprogram(struct hrtimer *timer,
{
return 0;
}
+static inline void hrtimer_raise_softirq(void) { }

#endif /* CONFIG_HIGH_RES_TIMERS */

@@ -850,7 +855,7 @@ hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
{
struct hrtimer_clock_base *base, *new_base;
unsigned long flags;
- int ret;
+ int ret, raise;

base = lock_hrtimer_base(timer, &flags);

@@ -884,8 +889,18 @@ hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
enqueue_hrtimer(timer, new_base,
new_base->cpu_base == &__get_cpu_var(hrtimer_bases));

+ /*
+ * The timer may be expired and moved to the cb_pending
+ * list. We can not raise the softirq with base lock held due
+ * to a possible deadlock with runqueue lock.
+ */
+ raise = timer->state == HRTIMER_STATE_PENDING;
+
unlock_hrtimer_base(timer, &flags);

+ if (raise)
+ hrtimer_raise_softirq();
+
return ret;
}
EXPORT_SYMBOL_GPL(hrtimer_start);
--
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