From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [RFC] IB/srp: Remove create_workqueue Date: Mon, 20 Jun 2016 14:59:22 -0400 Message-ID: <20160620185922.GQ3262@mtj.duckdns.org> References: <20160607181617.GA6556@Karyakshetra> <20160607192106.GY31708@htj.duckdns.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Bart Van Assche Cc: Bhaktipriya Shridhar , Doug Ledford , Sean Hefty , Hal Rosenstock , "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: linux-rdma@vger.kernel.org Hello, Bart. On Tue, Jun 07, 2016 at 01:00:13PM -0700, Bart Van Assche wrote: > > > > srp_remove_wq is used for SRP target port removal work only. This work is > > > > neither queued from inside a shrinker nor by the page writeback code so I > > > > think it is safe to drop WQ_MEM_RECLAIM. > > > > > > It should be able to use system_wq then. > > > > No. I have tried that but that resulted in a deadlock. > > See also commit bcc059103591 for the details. So, create_workqueue() limits concurrency to 1 per cpu and if you have a dependency between two work items and they get scheduled on the same cpu they can deadlock. system_wq doesn't have that restriction and should be fine, AFAICS. Thanks! -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html