Messages in this thread | | | Date | Thu, 28 Jul 2022 06:35:27 -1000 | From | Tejun Heo <> | Subject | Re: [RFC PATCH v2 1/2] workqueue: Unbind workers before sending them to exit() |
| |
On Thu, Jul 28, 2022 at 11:54:19AM +0100, Valentin Schneider wrote: > On 28/07/22 01:13, Lai Jiangshan wrote: > > Quick review before going to sleep. > > > > Thanks! > > > On Wed, Jul 27, 2022 at 7:54 PM Valentin Schneider <vschneid@redhat.com> wrote: > >> @@ -1806,8 +1806,10 @@ static void worker_enter_idle(struct worker *worker) > >> /* idle_list is LIFO */ > >> list_add(&worker->entry, &pool->idle_list); > >> > >> - if (too_many_workers(pool) && !timer_pending(&pool->idle_timer)) > >> - mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT); > >> + if (too_many_workers(pool) && !delayed_work_pending(&pool->idle_reaper_work)) > >> + mod_delayed_work(system_unbound_wq, > >> + &pool->idle_reaper_work, > >> + IDLE_WORKER_TIMEOUT); > > > > system_unbound_wq doesn't have a rescuer. > > > > A new workqueue with a rescuer needs to be created and used for > > this purpose. > > > > Right, I think it makes sense for those work items to be attached to a > WQ_MEM_RECLAIM workqueue. Should I add that as a workqueue-internal > thing?
I don't understand why this would need MEM_RECLAIM when it isn't sitting in the memory reclaim path. Nothing in mm side can wait on this.
> > Since WORKER_DIE is set, the worker can be possible freed now > > if there is another source to wake it up. > > > > My understanding for having reap_worker() be "safe" to use outside of > raw_spin_lock_irq(pool->lock) is that pool->idle_list is never accessed > outside of the pool->lock, and wake_up_worker() only wakes a worker that > is in that list. So with destroy_worker() detaching the worker from > pool->idle_list under pool->lock, I'm not aware of a codepath other than > reap_worker() that could wake it up.
There actually are spurious wakeups. We can't depend on there being no wakeups than ours.
Thanks.
-- tejun
| |