From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH v4 2/2] virtio_balloon: Use a workqueue instead of "vballoon" kthread Date: Sat, 2 Jan 2016 06:43:16 -0500 Message-ID: <20160102114316.GC3660@htj.duckdns.org> References: <1449236271-10133-1-git-send-email-pmladek@suse.com> <1449236271-10133-3-git-send-email-pmladek@suse.com> <20160101121432-mutt-send-email-mst@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20160101121432-mutt-send-email-mst@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: "Michael S. Tsirkin" Cc: Petr Mladek , Jiri Kosina , linux-kernel@vger.kernel.org, Petr Mladek , virtualization@lists.linux-foundation.org, Jeff Epler List-Id: virtualization@lists.linuxfoundation.org Hello, On Fri, Jan 01, 2016 at 12:18:17PM +0200, Michael S. Tsirkin wrote: > > My initial idea was to use a dedicated workqueue. Michael S. Tsirkin > > suggested using a system one. Tejun Heo confirmed that the system > > workqueue has a pretty high concurrency level (256) by default. > > Therefore we need not be afraid of too long blocking. > > Right but fill has a 1/5 second sleep on failure - *that* > is problematic for a system queue. Why so? As long as the maximum concurrently used workers are not high, 1/5 second or even a lot longer sleeps are completely fine. > > @@ -563,7 +534,7 @@ static void virtballoon_remove(struct virtio_device *vdev) > > struct virtio_balloon *vb = vdev->priv; > > > > unregister_oom_notifier(&vb->nb); > > - kthread_stop(vb->thread); > > + cancel_work_sync(&vb->wq_work); > > OK but since job requeues itself, cancelling like this might not be enough. As long as there's no further external queueing, cancel_work_sync() is guaranteed to kill a self-requeueing work item. Thanks. -- tejun