From 3b1618d24ec494094e1480a9a23d42381f689c3c Mon Sep 17 00:00:00 2001 From: Xuewen Yan Date: Wed, 10 Jan 2024 11:27:24 +0800 Subject: [PATCH] workqueue: Add rcu lock check at the end of work item execution BugLink: https://bugs.launchpad.net/bugs/2106770 [ Upstream commit 1a65a6d17cbc58e1aeffb2be962acce49efbef9c ] Currently the workqueue just checks the atomic and locking states after work execution ends. However, sometimes, a work item may not unlock rcu after acquiring rcu_read_lock(). And as a result, it would cause rcu stall, but the rcu stall warning can not dump the work func, because the work has finished. In order to quickly discover those works that do not call rcu_read_unlock() after rcu_read_lock(), add the rcu lock check. Use rcu_preempt_depth() to check the work's rcu status. Normally, this value is 0. If this value is bigger than 0, it means the work are still holding rcu lock. If so, print err info and the work func. tj: Reworded the description for clarity. Minor formatting tweak. Signed-off-by: Xuewen Yan Reviewed-by: Lai Jiangshan Reviewed-by: Waiman Long Signed-off-by: Tejun Heo Stable-dep-of: de35994ecd2d ("workqueue: Do not warn when cancelling WQ_MEM_RECLAIM work from !WQ_MEM_RECLAIM worker") Signed-off-by: Sasha Levin Signed-off-by: Manuel Diewald Signed-off-by: Mehmet Basaran --- kernel/workqueue.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 44eefab37d7f..f5f5a3dcb91b 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -2648,11 +2648,12 @@ __acquires(&pool->lock) lock_map_release(&lockdep_map); lock_map_release(&pwq->wq->lockdep_map); - if (unlikely(in_atomic() || lockdep_depth(current) > 0)) { - pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n" + if (unlikely(in_atomic() || lockdep_depth(current) > 0 || + rcu_preempt_depth() > 0)) { + pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d/%d\n" " last function: %ps\n", - current->comm, preempt_count(), task_pid_nr(current), - worker->current_func); + current->comm, preempt_count(), rcu_preempt_depth(), + task_pid_nr(current), worker->current_func); debug_show_held_locks(current); dump_stack(); }