6.6-stable review patch. If anyone has any objections, please let me know.
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From: Xuewen Yan xuewen.yan@unisoc.com
[ 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 xuewen.yan@unisoc.com Reviewed-by: Lai Jiangshan jiangshanlai@gmail.com Reviewed-by: Waiman Long longman@redhat.com Signed-off-by: Tejun Heo tj@kernel.org Stable-dep-of: de35994ecd2d ("workqueue: Do not warn when cancelling WQ_MEM_RECLAIM work from !WQ_MEM_RECLAIM worker") Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/workqueue.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 7fa1c7c9151a..2d85f232c675 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -2638,11 +2638,12 @@ __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(); }