The following commit has been merged into the locking/urgent branch of tip:

Commit-ID: d33d26036a0274b472299d7dcdaa5fb34329f91b Gitweb: https://git.kernel.org/tip/d33d26036a0274b472299d7dcdaa5fb34329f91b Author: Roland Xu mu001999@outlook.com AuthorDate: Thu, 15 Aug 2024 10:58:13 +08:00 Committer: Thomas Gleixner tglx@linutronix.de CommitterDate: Thu, 15 Aug 2024 15:38:53 +02:00

rtmutex: Drop rt_mutex::wait_lock before scheduling

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@ME0P300MB... --- kernel/locking/rtmutex.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 88d08ee..fba1229 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1644,6 +1644,7 @@ 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) { /* @@ -1656,10 +1657,10 @@ 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); rt_mutex_schedule(); @@ -1713,7 +1714,7 @@ 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); }

/*