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rtmutex: Drop rt_mutex::wait_lock before scheduling

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commit d33d26036a 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: 3d5c9340d1 ("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>
This commit is contained in:
Roland Xu 2024-08-15 10:58:13 +08:00 committed by Greg Kroah-Hartman
parent b322a385c0
commit 93f4465547
1 changed files with 5 additions and 4 deletions
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9
kernel/locking/rtmutex.c
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@ -1613,6 +1613,7 @@ static int __sched rt_mutex_slowlock_block(struct rt_mutex_base *lock,
}
static void __sched rt_mutex_handle_deadlock(int res, int detect_deadlock,
struct rt_mutex_base *lock,
struct rt_mutex_waiter *w)
{
/*
@ -1625,10 +1626,10 @@ static void __sched rt_mutex_handle_deadlock(int res, int detect_deadlock,
if (build_ww_mutex() && w->ww_ctx)
return;
/*
* Yell loudly and stop the task right here.
*/
raw_spin_unlock_irq(&lock->wait_lock);
WARN(1, "rtmutex deadlock detected\n");
while (1) {
set_current_state(TASK_INTERRUPTIBLE);
schedule();
@ -1680,7 +1681,7 @@ static int __sched __rt_mutex_slowlock(struct rt_mutex_base *lock,
} else {
__set_current_state(TASK_RUNNING);
remove_waiter(lock, waiter);
rt_mutex_handle_deadlock(ret, chwalk, waiter);
rt_mutex_handle_deadlock(ret, chwalk, lock, waiter);
}
/*