From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH repost for-3.9] pci: avoid work_on_cpu for nested SRIOV probes Date: Thu, 11 Apr 2013 23:30:53 +0300 Message-ID: <20130411203053.GC25515@redhat.com> References: <20130411153030.GA22743@redhat.com> <20130411180517.GJ17641@mtj.dyndns.org> <20130411185853.GE23301@redhat.com> <20130411190408.GM17641@mtj.dyndns.org> <20130411191717.GB25515@redhat.com> <20130411192005.GN17641@mtj.dyndns.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Or Gerlitz , Ming Lei , Greg Kroah-Hartman , David Miller , Roland Dreier , netdev , Yan Burman , Jack Morgenstein , Bjorn Helgaas , linux-pci@vger.kernel.org To: Tejun Heo Return-path: Received: from mx1.redhat.com ([209.132.183.28]:33226 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932875Ab3DKUbN (ORCPT ); Thu, 11 Apr 2013 16:31:13 -0400 Content-Disposition: inline In-Reply-To: <20130411192005.GN17641@mtj.dyndns.org> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, Apr 11, 2013 at 12:20:05PM -0700, Tejun Heo wrote: > On Thu, Apr 11, 2013 at 10:17:17PM +0300, Michael S. Tsirkin wrote: > > Hmm no, there's a real deadlock here: you are > > trying to flush from work1 from within work2 running > > on same workqueue. work2 can't event start running. > > The problem is not annotation. > > No, that has changed years ago with introduction of cmwq. System > workqueues are now expected to have high enough maximum concurrency to > not cause deadlock as long as memory for worker creation is available, > so as long as your work item doesn't directly sit in the memory > reclaim path, it's safe to flush a different work item running on the > same workqueue with sufficiently high max_active. > > Thanks. Okay, so you are saying it's a false-positive? Want to send a patch so Or can try it out? > -- > tejun