rt domain: don't arm the same release heap timer twice (bugfix)

If the timeout was realy close and the timing unfortunate, the
timer callback got invoked twice, with oopsing consequences.

1 files changed, 8 insertions, 13 deletions

diff --git a/litmus/rt_domain.c b/litmus/rt_domain.c
index f2e77f828d..e02ec03ca1 100644
--- a/litmus/rt_domain.c
+++ b/litmus/rt_domain.c
@@ -124,8 +124,6 @@ static void arm_release_timer(unsigned long _rt)
         struct list_head *pos, *safe;
         struct task_struct* t;
         struct release_heap* rh;
-        int armed;
-        lt_t release = 0;
 
         /* We only have to defend against the ISR since norq callbacks
          * are serialized.
@@ -146,29 +144,26 @@ static void arm_release_timer(unsigned long _rt)
                 rh = get_release_heap(rt, t);
                 heap_insert(rt->order, &rh->heap, tsk_rt(t)->heap_node);
                 TRACE_TASK(t, "arm_release_timer(): added to release heap\n");
-                if (rt->release_master == NO_CPU)
-                        armed = hrtimer_active(&rh->timer);
-                else
-                        armed = atomic_read(&rh->info.state)
-                                != HRTIMER_START_ON_INACTIVE;
-                release = rh->release_time;
                 spin_unlock_irqrestore(&rt->release_lock, flags);
 
-                /* activate timer if necessary */
-                if (!armed) {
+                /* To avoid arming the timer multiple times, we only let the
+                 * owner do the arming (which is the "first" task to reference
+                 * this release_heap anyway).
+                 */
+                if (rh == tsk_rt(t)->rel_heap) {
                         TRACE_TASK(t, "arming timer 0x%p\n", &rh->timer);
                         if (rt->release_master == NO_CPU)
                                 hrtimer_start(&rh->timer,
-                                              ns_to_ktime(release),
+                                              ns_to_ktime(rh->release_time),
                                               HRTIMER_MODE_ABS);
                         else
                                 hrtimer_start_on(rt->release_master,
                                                  &rh->info,
                                                  &rh->timer,
-                                                 ns_to_ktime(release),
+                                                 ns_to_ktime(rh->release_time),
                                                  HRTIMER_MODE_ABS);
                 } else
-                        TRACE_TASK(t, "timer already armed.\n");
+                        TRACE_TASK(t, "0x%p is not my timer\n", &rh->timer);
         }
 }