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workqueue: Add rcu lock check at the end of work item execution

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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>
This commit is contained in:
Xuewen Yan 2024-01-10 11:27:24 +08:00 committed by Tejun Heo
parent 85f0ab43f9
commit 1a65a6d17c
1 changed files with 5 additions and 4 deletions
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9
kernel/workqueue.c
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@ -2640,11 +2640,12 @@ __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();
}