Gregory Haskins wrote:
@@ -732,14 +741,15 @@ rt_spin_lock_slowlock(struct rt_mutex *lock)
debug_rt_mutex_print_deadlock(&waiter);
- schedule_rt_mutex(lock);
+ update_current(TASK_UNINTERRUPTIBLE, &saved_state);
I have a question for everyone out there about this particular part of
the code. Patch 6/14 adds an optimization that is predicated on the
order in which we modify the state==TASK_UNINTERRUPTIBLE vs reading the
waiter.task below.
My assumption is that the xchg() (inside update_current()) acts as an
effective wmb(). If xchg() does not have this property, then this code
is broken and patch 6/14 should also add a:
+ smp_wmb();
+ if (waiter.task)
+ schedule_rt_mutex(lock);
+ else
+ update_current(TASK_RUNNING_MUTEX, &saved_state);
spin_lock_irqsave(&lock->wait_lock, flags);
current->flags |= saved_flags;
current->lock_depth = saved_lock_depth;
- state = xchg(¤t->state, TASK_UNINTERRUPTIBLE);
- if (unlikely(state == TASK_RUNNING))
- saved_state = TASK_RUNNING;
Does anyone know the answer to this?
Regards,
-Greg
-
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