[PATCH AUTOSEL 3.18 11/98] Revert "drm/i915: Fix mutex->owner inspection race under DEBUG_MUTEXES"

From: Sasha Levin
Date: Thu Oct 25 2018 - 10:30:09 EST

From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>

[ Upstream commit a50940510e94f5fb65ffd79877a60592d85598a9 ]

The core fix was applied in

commit a63b03e2d2477586440741677ecac45bcf28d7b1
Author: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Date: Tue Jan 6 10:29:35 2015 +0000

mutex: Always clear owner field upon mutex_unlock()

(note the absence of stable@ tag)

so we can now revert our band-aid commit 226e5ae9e5f910 for -next.

Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Jani Nikula <jani.nikula@xxxxxxxxx>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/gpu/drm/i915/i915_gem.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index d88dbedeaa77..d0f0a7943d88 100644
--- 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;
/* Since UP may be pre-empted, we cannot assume that we own the lock */