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

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Date:   Thu, 25 Oct 2018 10:17:26 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     stable@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Chris Wilson <chris@...is-wilson.co.uk>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Jani Nikula <jani.nikula@...el.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 3.18 11/98] Revert "drm/i915: Fix mutex->owner inspection race under DEBUG_MUTEXES"

From: Chris Wilson <chris@...is-wilson.co.uk>

[ Upstream commit a50940510e94f5fb65ffd79877a60592d85598a9 ]

The core fix was applied in

commit a63b03e2d2477586440741677ecac45bcf28d7b1
Author: Chris Wilson <chris@...is-wilson.co.uk>
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@...is-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@...ll.ch>
Cc: Jani Nikula <jani.nikula@...el.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@...el.com>
Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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;
 #else
 	/* Since UP may be pre-empted, we cannot assume that we own the lock */
-- 
2.17.1