From: Lai Jiangshan <jiangshanlai@gmail.com>
To: Valentin Schneider <vschneid@redhat.com>
Cc: Tejun Heo <tj@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Frederic Weisbecker <frederic@kernel.org>,
Juri Lelli <juri.lelli@redhat.com>, Phil Auld <pauld@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [RFC PATCH] workqueue: Unbind workers before sending them to exit()
Date: Wed, 27 Jul 2022 16:55:09 +0800 [thread overview]
Message-ID: <CAJhGHyDQ537NatcsTFAsTz=pKadnCtTYfvK_tXE=Z5oRp5FQyA@mail.gmail.com> (raw)
In-Reply-To: <CAJhGHyAEHFbcqzVbBRHoFcRYJ+M9cf87WwV2u=V4=Acrgp-gkQ@mail.gmail.com>
On Wed, Jul 27, 2022 at 2:30 PM Lai Jiangshan <jiangshanlai@gmail.com> wrote:
> >
> > >
> > > What hasn't changed much between my attempts is transferring to-be-destroyed
> > > kworkers from their pool->idle_list to a reaper_list which is walked by
> > > *something* that does unbind+wakeup. AFAIA as long as the kworker is off
> > > the pool->idle_list we can play with it (i.e. unbind+wake) off the
> > > pool->lock.
> > >
> > > It's the *something* that's annoying to get right, I don't want it to be
> > > overly complicated given most users are probably not impacted by what I'm
> > > trying to fix, but I'm getting the feeling it should still be a per-pool
> > > kthread. I toyed with a single reaper kthread but a central synchronization
> > > for all the pools feels like a stupid overhead.
> >
> > I think fixing it in the workqueue.c is complicated.
> >
> > Nevertheless, I will also try to fix it inside workqueue only to see
> > what will come up.
>
> I'm going to kind of revert 3347fc9f36e7 ("workqueue: destroy worker
> directly in the idle timeout handler"), so that we can have a sleepable
> destroy_worker().
>
It is not a good idea. The woken up manager might still be in
the isolated CPU.
On Wed, Jul 27, 2022 at 6:59 AM Tejun Heo <tj@kernel.org> wrote:
>
> I mean, whatever works works but let's please keep it as minimal as
> possible. Why does it need dedicated kthreads in the first place? Wouldn't
> scheduling an unbound work item work just as well?
>
Scheduling an unbound work item will work well.
next prev parent reply other threads:[~2022-07-27 8:55 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-19 16:57 [RFC PATCH] workqueue: Unbind workers before sending them to exit() Valentin Schneider
2022-07-20 17:54 ` Marcelo Tosatti
2022-07-20 18:03 ` Tejun Heo
2022-07-21 3:35 ` Lai Jiangshan
2022-07-21 13:53 ` Valentin Schneider
2022-07-23 5:16 ` Tejun Heo
2022-07-25 10:21 ` Valentin Schneider
2022-07-26 17:30 ` Tejun Heo
2022-07-26 20:36 ` Valentin Schneider
2022-07-26 22:59 ` Tejun Heo
2022-07-27 5:38 ` Lai Jiangshan
2022-07-27 6:30 ` Lai Jiangshan
2022-07-27 8:55 ` Lai Jiangshan [this message]
2022-07-27 9:22 ` Valentin Schneider
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