| Subject: rtmutex: Handle non enqueued waiters gracefully |
| From: Thomas Gleixner <tglx@linutronix.de> |
| Date: Fri, 06 Nov 2015 18:51:03 +0100 |
| |
| Yimin debugged that in case of a PI wakeup in progress when |
| rt_mutex_start_proxy_lock() calls task_blocks_on_rt_mutex() the latter |
| returns -EAGAIN and in consequence the remove_waiter() call runs into |
| a BUG_ON() because there is nothing to remove. |
| |
| Guard it with rt_mutex_has_waiters(). This is a quick fix which is |
| easy to backport. The proper fix is to have a central check in |
| remove_waiter() so we can call it unconditionally. |
| |
| Reported-and-debugged-by: Yimin Deng <yimin11.deng@gmail.com> |
| Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
| Cc: stable-rt@vger.kernel.org |
| |
| --- |
| kernel/locking/rtmutex.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/kernel/locking/rtmutex.c |
| +++ b/kernel/locking/rtmutex.c |
| @@ -1707,7 +1707,7 @@ int __rt_mutex_start_proxy_lock(struct r |
| ret = 0; |
| } |
| |
| - if (unlikely(ret)) |
| + if (ret && rt_mutex_has_waiters(lock)) |
| remove_waiter(lock, waiter); |
| |
| debug_rt_mutex_print_deadlock(waiter); |
