Revert "Revert "drm/i915: Fix mutex->owner inspection race under DEBUG_MUTEXES""

This reverts commit bc07ee33284ac6e6872d5efad1b321ec0b7b46a4. Which is
upstream commit a50940510e94f5fb65ffd79877a60592d85598a9.

This revert relies on upstream commit a63b03e2d24 ("mutex: Always clear
owner field upon mutex_unlock()") being in the tree, but that commit
should not be backported.

Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index d0f0a79..d88dbed 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -5144,7 +5144,7 @@ static bool mutex_is_locked_by(struct mutex *mutex, struct task_struct *task)
        if (!mutex_is_locked(mutex))
                return false;
 
-#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_MUTEXES)
+#if defined(CONFIG_SMP) && !defined(CONFIG_DEBUG_MUTEXES)
        return mutex->owner == task;
 #else
        /* Since UP may be pre-empted, we cannot assume that we own the lock */