On Mon, Apr 27, 2020 at 11:43:58AM -0700, Suren Baghdasaryan wrote: > A number of kthread-related functions indirectly take task_struct->pi_lock > while holding worker->lock in the call chain like this: > spin_lock(&worker->lock) > kthread_insert_work > wake_up_process > try_to_wake_up > raw_spin_lock_irqsave(&p->pi_lock, flags) > > This lock dependency exists whenever kthread_insert_work is called either > directly or indirectly via __kthread_queue_delayed_work in the following > functions: > kthread_queue_work > kthread_delayed_work_timer_fn > kthread_queue_delayed_work > kthread_flush_work > kthread_mod_delayed_work > > This creates possibilities for circular dependencies like the one reported > at: https://lkml.org/lkml/2020/4/24/954
Please, do not use lkml.org links. Also, ideally, we'd pull that kthread_queue_delayed_work() out from under rq->lock. In fact, looking at it, WTH is the delayed branch of kthread_queue_delayed_work() under that lock? That whole delayed_work_list thing smells like bong-hits.
