diff options
Diffstat (limited to 'debian/patches-rt/0352-workqueue-Fix-deadlock-due-to-recursive-locking-of-p.patch')
| -rw-r--r-- | debian/patches-rt/0352-workqueue-Fix-deadlock-due-to-recursive-locking-of-p.patch | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/debian/patches-rt/0352-workqueue-Fix-deadlock-due-to-recursive-locking-of-p.patch b/debian/patches-rt/0352-workqueue-Fix-deadlock-due-to-recursive-locking-of-p.patch new file mode 100644 index 000000000..e5cbdc585 --- /dev/null +++ b/debian/patches-rt/0352-workqueue-Fix-deadlock-due-to-recursive-locking-of-p.patch @@ -0,0 +1,68 @@ +From: "Brennan Lamoreaux (VMware)" <brennanlamoreaux@gmail.com> +Date: Tue, 28 Feb 2023 14:49:38 -0800 +Subject: [PATCH 352/353] workqueue: Fix deadlock due to recursive locking of + pool->lock +Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=813609bc5c58e47a292c3e8cbe961c494e4670a1 + +Upstream commit d8bb65ab70f7 ("workqueue: Use rcuwait for wq_manager_wait") +replaced the waitqueue with rcuwait in the workqueue code. This change +involved removing the acquisition of pool->lock in put_unbound_pool(), +as it also adds the function wq_manager_inactive() which acquires this same +lock and is called one line later as a parameter to rcu_wait_event(). + +However, the backport of this commit in the PREEMPT_RT patchset +4.19.255-rt114 (patch 347) missed the removal of the acquisition of +pool->lock in put_unbound_pool(). This leads to a deadlock due to +recursive locking of pool->lock, as shown below in lockdep: + +[ 252.083713] WARNING: possible recursive locking detected +[ 252.083718] 4.19.269-3.ph3-rt #1-photon Not tainted +[ 252.083721] -------------------------------------------- +[ 252.083733] kworker/2:0/33 is trying to acquire lock: +[ 252.083747] 000000000b7b1ceb (&pool->lock/1){....}, at: +put_unbound_pool+0x10d/0x260 + +[ 252.083857] + but task is already holding lock: +[ 252.083860] 000000000b7b1ceb (&pool->lock/1){....}, at: +put_unbound_pool+0xbd/0x260 + +[ 252.083876] + other info that might help us debug this: +[ 252.083897] Possible unsafe locking scenario: + +[ 252.083900] CPU0 +[ 252.083903] ---- +[ 252.083904] lock(&pool->lock/1); +[ 252.083911] lock(&pool->lock/1); +[ 252.083919] + *** DEADLOCK *** + +[ 252.083921] May be due to missing lock nesting notation + +Fix this deadlock by removing the pool->lock acquisition in +put_unbound_pool(). + +Signed-off-by: Brennan Lamoreaux (VMware) <brennanlamoreaux@gmail.com> +Cc: Daniel Wagner <wagi@monom.org> +Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Cc: Tejun Heo <tj@kernel.org> +Reviewed-by: Srivatsa S. Bhat (VMware) <srivatsa@csail.mit.edu> +Link: https://lore.kernel.org/r/20230228224938.88035-1-brennanlamoreaux@gmail.com +Signed-off-by: Daniel Wagner <wagi@monom.org> +--- + kernel/workqueue.c | 1 - + 1 file changed, 1 deletion(-) + +diff --git a/kernel/workqueue.c b/kernel/workqueue.c +index a9f3cc02bdc1..55ebdd56a5de 100644 +--- a/kernel/workqueue.c ++++ b/kernel/workqueue.c +@@ -3394,7 +3394,6 @@ static void put_unbound_pool(struct worker_pool *pool) + * Because of how wq_manager_inactive() works, we will hold the + * spinlock after a successful wait. + */ +- raw_spin_lock_irq(&pool->lock); + rcuwait_wait_event(&manager_wait, wq_manager_inactive(pool), + TASK_UNINTERRUPTIBLE); + pool->flags |= POOL_MANAGER_ACTIVE; |