The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.19.y git checkout FETCH_HEAD git cherry-pick -x d33d26036a0274b472299d7dcdaa5fb34329f91b # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024090850-nuclear-radar-ea2b@gregkh' --subject-prefix 'PATCH 4.19.y' HEAD^..

Possible dependencies:

d33d26036a02 ("rtmutex: Drop rt_mutex::wait_lock before scheduling") add461325ec5 ("locking/rtmutex: Extend the rtmutex core to support ww_mutex") 1c143c4b65da ("locking/rtmutex: Provide the spin/rwlock core lock function") e17ba59b7e8e ("locking/rtmutex: Guard regular sleeping locks specific functions") 7980aa397cc0 ("locking/rtmutex: Use rt_mutex_wake_q_head") c014ef69b3ac ("locking/rtmutex: Add wake_state to rt_mutex_waiter") 42254105dfe8 ("locking/rwsem: Add rtmutex based R/W semaphore implementation") ebbdc41e90ff ("locking/rtmutex: Provide rt_mutex_slowlock_locked()") 830e6acc8a1c ("locking/rtmutex: Split out the inner parts of 'struct rtmutex'") 531ae4b06a73 ("locking/rtmutex: Split API from implementation") 785159301bed ("locking/rtmutex: Convert macros to inlines") b41cda037655 ("locking/rtmutex: Set proper wait context for lockdep") 2f064a59a11f ("sched: Change task_struct::state") d6c23bb3a2ad ("sched: Add get_current_state()") b03fbd4ff24c ("sched: Introduce task_is_running()") a9e906b71f96 ("Merge branch 'sched/urgent' into sched/core, to pick up fixes")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From d33d26036a0274b472299d7dcdaa5fb34329f91b Mon Sep 17 00:00:00 2001 From: Roland Xu mu001999@outlook.com Date: Thu, 15 Aug 2024 10:58:13 +0800 Subject: [PATCH] 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...

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 88d08eeb8bc0..fba1229f1de6 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); }

/*