[PATCH RT 19/36] rtmutex: enable deadlock detection in ww_mutex_lock functions

[Steven Rostedt]

3.12.38-rt53-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Gustavo Bittencourt <gbitten@xxxxxxxxx>

The functions ww_mutex_lock_interruptible and ww_mutex_lock should return -EDEADLK when faced with
a deadlock. To do so, the paramenter detect_deadlock in rt_mutex_slowlock must be TRUE.
This patch corrects potential deadlocks when running PREEMPT_RT with nouveau driver.

Cc: stable-rt@xxxxxxxxxxxxxxx
Signed-off-by: Gustavo Bittencourt <gbitten@xxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 kernel/rtmutex.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
index 76cb88027fc2..e8a6555a670a 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -2166,7 +2166,8 @@ __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ww_c
 	might_sleep();
 
 	mutex_acquire_nest(&lock->base.dep_map, 0, 0, &ww_ctx->dep_map, _RET_IP_);
-	ret = rt_mutex_slowlock(&lock->base.lock, TASK_INTERRUPTIBLE, NULL, 0, ww_ctx);
+	ret = rt_mutex_slowlock(&lock->base.lock, TASK_INTERRUPTIBLE, NULL,
+				RT_MUTEX_FULL_CHAINWALK, ww_ctx);
 	if (ret)
 		mutex_release(&lock->base.dep_map, 1, _RET_IP_);
 	else if (!ret && ww_ctx->acquired > 1)
@@ -2184,7 +2185,8 @@ __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ww_ctx)
 	might_sleep();
 
 	mutex_acquire_nest(&lock->base.dep_map, 0, 0, &ww_ctx->dep_map, _RET_IP_);
-	ret = rt_mutex_slowlock(&lock->base.lock, TASK_UNINTERRUPTIBLE, NULL, 0, ww_ctx);
+	ret = rt_mutex_slowlock(&lock->base.lock, TASK_UNINTERRUPTIBLE, NULL,
+				RT_MUTEX_FULL_CHAINWALK, ww_ctx);
 	if (ret)
 		mutex_release(&lock->base.dep_map, 1, _RET_IP_);
 	else if (!ret && ww_ctx->acquired > 1)
-- 
2.1.4


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