rtmutex: Drop rt_mutex::wait_lock before scheduling

commit d33d26036a0274b472299d7dcdaa5fb34329f91b upstream.

rt_mutex_handle_deadlock() is called with rt_mutex::wait_lock held.  In the
good case it returns with the lock held and in the deadlock case it emits a
warning and goes into an endless scheduling loop with the lock held, which
triggers the 'scheduling in atomic' warning.

Unlock rt_mutex::wait_lock in the dead lock case before issuing the warning
and dropping into the schedule for ever loop.

[ tglx: Moved unlock before the WARN(), removed the pointless comment,
  	massaged changelog, added Fixes tag ]

Fixes: 3d5c9340d194 ("rtmutex: Handle deadlock detection smarter")
Signed-off-by: Roland Xu <mu001999@outlook.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/ME0P300MB063599BEF0743B8FA339C2CECC802@ME0P300MB0635.AUSP300.PROD.OUTLOOK.COM
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index f00dd928fc7113c6a31aaa05d6214c08f3fee201..c6a2dafd4a3b4d9266d835e76f18e5919a684ec8 100644 (file)
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1202,6 +1202,7 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state,
 }
 
 static void rt_mutex_handle_deadlock(int res, int detect_deadlock,
+                                    struct rt_mutex *lock,
                                     struct rt_mutex_waiter *w)
 {
        /*
@@ -1211,6 +1212,7 @@ static void rt_mutex_handle_deadlock(int res, int detect_deadlock,
        if (res != -EDEADLOCK || detect_deadlock)
                return;
 
+       raw_spin_unlock_irq(&lock->wait_lock);
        /*
         * Yell lowdly and stop the task right here.
         */
@@ -1266,7 +1268,7 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state,
        if (unlikely(ret)) {
                __set_current_state(TASK_RUNNING);
                remove_waiter(lock, &waiter);
-               rt_mutex_handle_deadlock(ret, chwalk, &waiter);
+               rt_mutex_handle_deadlock(ret, chwalk, lock, &waiter);
        }
 
        /*