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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2009-01-05 11:28:22 +0100
committerIngo Molnar <mingo@elte.hu>2009-01-05 13:14:33 +0100
commita6037b61c2f5fc99c57c15b26d7cfa58bbb34008 (patch)
treeb076de5cc8a75e4227f96dda31a0daa6e895579b
parent731a55ba0f17064f85903b7bf8e24849ec6cfa20 (diff)
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hrtimer: fix recursion deadlock by re-introducing the softirq
Impact: fix rare runtime deadlock There are a few sites that do: spin_lock_irq(&foo) hrtimer_start(&bar) __run_hrtimer(&bar) func() spin_lock(&foo) which obviously deadlocks. In order to avoid this, never call __run_hrtimer() from hrtimer_start*() context, but instead defer this to softirq context. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--include/linux/interrupt.h3
-rw-r--r--kernel/hrtimer.c60
2 files changed, 29 insertions, 34 deletions
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 0702c4d7bdf..2062833f5f7 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -253,7 +253,8 @@ enum
BLOCK_SOFTIRQ,
TASKLET_SOFTIRQ,
SCHED_SOFTIRQ,
- RCU_SOFTIRQ, /* Preferable RCU should always be the last softirq */
+ HRTIMER_SOFTIRQ,
+ RCU_SOFTIRQ, /* Preferable RCU should always be the last softirq */
NR_SOFTIRQS
};
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 8010a67cead..b68e98f4e4c 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -634,7 +634,6 @@ static inline void hrtimer_init_timer_hres(struct hrtimer *timer)
{
}
-static void __run_hrtimer(struct hrtimer *timer);
/*
* When High resolution timers are active, try to reprogram. Note, that in case
@@ -646,13 +645,9 @@ static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
struct hrtimer_clock_base *base)
{
if (base->cpu_base->hres_active && hrtimer_reprogram(timer, base)) {
- /*
- * XXX: recursion check?
- * hrtimer_forward() should round up with timer granularity
- * so that we never get into inf recursion here,
- * it doesn't do that though
- */
- __run_hrtimer(timer);
+ spin_unlock(&base->cpu_base->lock);
+ raise_softirq_irqoff(HRTIMER_SOFTIRQ);
+ spin_lock(&base->cpu_base->lock);
return 1;
}
return 0;
@@ -705,11 +700,6 @@ static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
}
static inline void hrtimer_init_hres(struct hrtimer_cpu_base *base) { }
static inline void hrtimer_init_timer_hres(struct hrtimer *timer) { }
-static inline int hrtimer_reprogram(struct hrtimer *timer,
- struct hrtimer_clock_base *base)
-{
- return 0;
-}
#endif /* CONFIG_HIGH_RES_TIMERS */
@@ -780,9 +770,11 @@ EXPORT_SYMBOL_GPL(hrtimer_forward);
*
* The timer is inserted in expiry order. Insertion into the
* red black tree is O(log(n)). Must hold the base lock.
+ *
+ * Returns 1 when the new timer is the leftmost timer in the tree.
*/
-static void enqueue_hrtimer(struct hrtimer *timer,
- struct hrtimer_clock_base *base, int reprogram)
+static int enqueue_hrtimer(struct hrtimer *timer,
+ struct hrtimer_clock_base *base)
{
struct rb_node **link = &base->active.rb_node;
struct rb_node *parent = NULL;
@@ -814,20 +806,8 @@ static void enqueue_hrtimer(struct hrtimer *timer,
* Insert the timer to the rbtree and check whether it
* replaces the first pending timer
*/
- if (leftmost) {
- /*
- * Reprogram the clock event device. When the timer is already
- * expired hrtimer_enqueue_reprogram has either called the
- * callback or added it to the pending list and raised the
- * softirq.
- *
- * This is a NOP for !HIGHRES
- */
- if (reprogram && hrtimer_enqueue_reprogram(timer, base))
- return;
-
+ if (leftmost)
base->first = &timer->node;
- }
rb_link_node(&timer->node, parent, link);
rb_insert_color(&timer->node, &base->active);
@@ -836,6 +816,8 @@ static void enqueue_hrtimer(struct hrtimer *timer,
* state of a possibly running callback.
*/
timer->state |= HRTIMER_STATE_ENQUEUED;
+
+ return leftmost;
}
/*
@@ -912,7 +894,7 @@ hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim, unsigned long delta_n
{
struct hrtimer_clock_base *base, *new_base;
unsigned long flags;
- int ret;
+ int ret, leftmost;
base = lock_hrtimer_base(timer, &flags);
@@ -940,12 +922,16 @@ hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim, unsigned long delta_n
timer_stats_hrtimer_set_start_info(timer);
+ leftmost = enqueue_hrtimer(timer, new_base);
+
/*
* Only allow reprogramming if the new base is on this CPU.
* (it might still be on another CPU if the timer was pending)
+ *
+ * XXX send_remote_softirq() ?
*/
- enqueue_hrtimer(timer, new_base,
- new_base->cpu_base == &__get_cpu_var(hrtimer_bases));
+ if (leftmost && new_base->cpu_base == &__get_cpu_var(hrtimer_bases))
+ hrtimer_enqueue_reprogram(timer, new_base);
unlock_hrtimer_base(timer, &flags);
@@ -1163,7 +1149,7 @@ static void __run_hrtimer(struct hrtimer *timer)
*/
if (restart != HRTIMER_NORESTART) {
BUG_ON(timer->state != HRTIMER_STATE_CALLBACK);
- enqueue_hrtimer(timer, base, 0);
+ enqueue_hrtimer(timer, base);
}
timer->state &= ~HRTIMER_STATE_CALLBACK;
}
@@ -1277,6 +1263,11 @@ void hrtimer_peek_ahead_timers(void)
local_irq_restore(flags);
}
+static void run_hrtimer_softirq(struct softirq_action *h)
+{
+ hrtimer_peek_ahead_timers();
+}
+
#endif /* CONFIG_HIGH_RES_TIMERS */
/*
@@ -1532,7 +1523,7 @@ static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
* is done, which will run all expired timers and re-programm
* the timer device.
*/
- enqueue_hrtimer(timer, new_base, 0);
+ enqueue_hrtimer(timer, new_base);
/* Clear the migration state bit */
timer->state &= ~HRTIMER_STATE_MIGRATE;
@@ -1610,6 +1601,9 @@ void __init hrtimers_init(void)
hrtimer_cpu_notify(&hrtimers_nb, (unsigned long)CPU_UP_PREPARE,
(void *)(long)smp_processor_id());
register_cpu_notifier(&hrtimers_nb);
+#ifdef CONFIG_HIGH_RES_TIMERS
+ open_softirq(HRTIMER_SOFTIRQ, run_hrtimer_softirq);
+#endif
}
/**