> __visible __used noinline > @@ -730,6 +744,23 @@ __mutex_unlock_common_slowpath(struct mutex *lock, int > nested) > if (__mutex_slowpath_needs_to_unlock()) > atomic_set(&lock->count, 1); > > +/* > + * Skipping the mutex_has_owner() check when DEBUG, allows us to > + * avoid taking the wait_lock in order to do not call mutex_release() > + * and debug_mutex_unlock() when !DEBUG. This can otherwise result in > + * deadlocks when another task enters the lock's slowpath in mutex_lock(). > + */ > +#ifndef CONFIG_DEBUG_MUTEXES > + /* > + * Abort the wakeup operation if there is an another mutex owner, as the > + * lock was stolen. mutex_unlock() should have cleared the owner field > + * before calling this function. If that field is now set, another task > + * must have acquired the mutex. > + */ > + if (mutex_has_owner(lock)) > + return;
Would we need the mutex lock count to eventually get set to a negative value if there are waiters? An optimistic spinner can get the lock and set lock->count to 0. Then the lock count might remain 0 since a waiter might not get waken up here to try-lock and set lock->count to -1 if it goes back to sleep in the lock path. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
