From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751163AbcCXTjT (ORCPT ); Thu, 24 Mar 2016 15:39:19 -0400 Received: from mail-yw0-f178.google.com ([209.85.161.178]:34407 "EHLO mail-yw0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750724AbcCXTjR (ORCPT ); Thu, 24 Mar 2016 15:39:17 -0400 Date: Thu, 24 Mar 2016 15:39:14 -0400 From: Tejun Heo To: nick Cc: jiangshanlai@gmail.com, linux-kernel@vger.kernel.org, Thomas Gleixner Subject: Re: Workqueue change with commit id,1bd04bf6f breaks mpt3sas scsi driver Message-ID: <20160324193914.GC7822@mtj.duckdns.org> References: <56F350C0.5070000@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56F350C0.5070000@gmail.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (cc'ing Thomas) Hello, On Wed, Mar 23, 2016 at 10:28:16PM -0400, nick wrote: > Seems that commit id, 1bd04bf6f breaks the mpt3sas driver according to this bug report: > https://bugzilla.kernel.org/show_bug.cgi?id=114611. Seems that the driver is fine as > have inspection all the driver functions are wrappers around queue_delayed_work and > according to the person's debugging this commit breaks it. However they are not sure > if it's the driver or the timer subsystem. I am assuming it's the timer subsystem as > the driver is just using wrapper functions around core workqueue functions with irqs > disabled and a spin lock held. Hmmm... 1bd04bf6f68d ("timer: Remove FIFO "guarantee"") doesn't look like an easy change to undo and it sounds like the driver was already (subtly) broken even before the commit given that ordered workqueues are not affine to any CPU and timer expirations across different CPUs aren't strictly ordered. Unfortunately, the only way forward seems to be implementing ordering from the driver's side. Thanks. -- tejun