All of lore.kernel.org
 help / color / mirror / Atom feed
From: Tejun Heo <tj@kernel.org>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jiri Kosina <jkosina@suse.cz>,
	linux-kernel@vger.kernel.org, Petr Mladek <pmladek@suse.cz>,
	virtualization@lists.linux-foundation.org,
	Jeff Epler <jepler@unpythonic.net>
Subject: Re: [PATCH v3] virtio_balloon: Convert "vballoon" kthread into a workqueue
Date: Thu, 20 Nov 2014 11:49:33 -0500	[thread overview]
Message-ID: <20141120164933.GL14877@htj.dyndns.org> (raw)
In-Reply-To: <20141120164711.GA7495@redhat.com>

On Thu, Nov 20, 2014 at 06:47:11PM +0200, Michael S. Tsirkin wrote:
> > There's cancel_work_sync() to stop the self-requeueing ones.
> 
> What happens if queue_work runs while cancel_work_sync is in progress?
> Does it fail to queue?

cancel_work_sync() is guaranteed to take self-requeueing work items no
matter when it's called or what's going on.  External (non-self)
queueings of course should be stopped in other ways.

> > > From that POV a dedicated WQ kept it simple.
> > 
> > A dedicated wq doesn't do anything for that.  You can't shut down a
> > workqueue with a pending work item on it.  destroy_workqueue() will
> > try to drain the target wq, warn if it doesn't finish in certain
> > number of iterations and just keep trying indefinitely.
> > 
> > Thanks.
> 
> Right, so eventually we'll stop requeueuing and it will succeed?

Yeah, sure, it's a silly reason to use a separate workqueue tho.
Don't do it that way.

Thanks.

-- 
tejun

WARNING: multiple messages have this Message-ID (diff)
From: Tejun Heo <tj@kernel.org>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Petr Mladek <pmladek@suse.cz>,
	Rusty Russell <rusty@rustcorp.com.au>,
	Jeff Epler <jepler@unpythonic.net>, Jiri Kosina <jkosina@suse.cz>,
	virtualization@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] virtio_balloon: Convert "vballoon" kthread into a workqueue
Date: Thu, 20 Nov 2014 11:49:33 -0500	[thread overview]
Message-ID: <20141120164933.GL14877@htj.dyndns.org> (raw)
In-Reply-To: <20141120164711.GA7495@redhat.com>

On Thu, Nov 20, 2014 at 06:47:11PM +0200, Michael S. Tsirkin wrote:
> > There's cancel_work_sync() to stop the self-requeueing ones.
> 
> What happens if queue_work runs while cancel_work_sync is in progress?
> Does it fail to queue?

cancel_work_sync() is guaranteed to take self-requeueing work items no
matter when it's called or what's going on.  External (non-self)
queueings of course should be stopped in other ways.

> > > From that POV a dedicated WQ kept it simple.
> > 
> > A dedicated wq doesn't do anything for that.  You can't shut down a
> > workqueue with a pending work item on it.  destroy_workqueue() will
> > try to drain the target wq, warn if it doesn't finish in certain
> > number of iterations and just keep trying indefinitely.
> > 
> > Thanks.
> 
> Right, so eventually we'll stop requeueuing and it will succeed?

Yeah, sure, it's a silly reason to use a separate workqueue tho.
Don't do it that way.

Thanks.

-- 
tejun

  reply	other threads:[~2014-11-20 16:49 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-11-20 16:03 [PATCH v3] virtio_balloon: Convert "vballoon" kthread into a workqueue Petr Mladek
2014-11-20 16:03 ` Petr Mladek
2014-11-20 16:07 ` Tejun Heo
2014-11-20 16:07   ` Tejun Heo
2014-11-20 16:25   ` Michael S. Tsirkin
2014-11-20 16:25     ` Michael S. Tsirkin
2014-11-20 16:26     ` Michael S. Tsirkin
2014-11-20 16:26       ` Michael S. Tsirkin
2014-11-20 16:29       ` Tejun Heo
2014-11-20 16:29         ` Tejun Heo
2014-11-20 16:47         ` Michael S. Tsirkin
2014-11-20 16:47           ` Michael S. Tsirkin
2014-11-20 16:49           ` Tejun Heo [this message]
2014-11-20 16:49             ` Tejun Heo
2014-11-20 16:50             ` Tejun Heo
2014-11-20 16:50               ` Tejun Heo
2014-11-20 16:55             ` Michael S. Tsirkin
2014-11-20 16:55               ` Michael S. Tsirkin
2014-11-20 16:55         ` Petr Mladek
2014-11-20 16:55           ` Petr Mladek
2014-11-20 17:00           ` Michael S. Tsirkin
2014-11-20 17:00             ` Michael S. Tsirkin
2014-11-20 17:17             ` Petr Mladek
2014-11-20 17:17               ` Petr Mladek

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20141120164933.GL14877@htj.dyndns.org \
    --to=tj@kernel.org \
    --cc=jepler@unpythonic.net \
    --cc=jkosina@suse.cz \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mst@redhat.com \
    --cc=pmladek@suse.cz \
    --cc=virtualization@lists.linux-foundation.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.