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

Steven Rostedt
2015-03-12T19:28:36Z

[-- Attachment #1: 0019-rtmutex-enable-deadlock-detection-in-ww_mutex_lock-f.patch --]
[-- Type: text/plain, Size: 1842 bytes --]

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

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

From: Gustavo Bittencourt <gbitten@gmail.com>

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@vger.kernel.org
Signed-off-by: Gustavo Bittencourt <gbitten@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
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