Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761719AbZAHS2T (ORCPT ); Thu, 8 Jan 2009 13:28:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757158AbZAHS2C (ORCPT ); Thu, 8 Jan 2009 13:28:02 -0500 Received: from rcsinet11.oracle.com ([148.87.113.123]:56230 "EHLO rgminet11.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755222AbZAHS17 (ORCPT ); Thu, 8 Jan 2009 13:27:59 -0500 Subject: Re: [PATCH -v7][RFC]: mutex: implement adaptive spinning From: Chris Mason To: Linus Torvalds Cc: Steven Rostedt , Peter Zijlstra , Ingo Molnar , paulmck@linux.vnet.ibm.com, Gregory Haskins , Matthew Wilcox , Andi Kleen , Andrew Morton , Linux Kernel Mailing List , linux-fsdevel , linux-btrfs , Thomas Gleixner , Nick Piggin , Peter Morreale , Sven Dietrich In-Reply-To: References: <1231347442.11687.344.camel@twins> <1231365115.11687.361.camel@twins> <1231366716.11687.377.camel@twins> <1231408718.11687.400.camel@twins> <20090108141808.GC11629@elte.hu> <1231426014.11687.456.camel@twins> <1231434515.14304.27.camel@think.oraclecorp.com> Content-Type: text/plain Date: Thu, 08 Jan 2009 13:27:14 -0500 Message-Id: <1231439234.14304.33.camel@think.oraclecorp.com> Mime-Version: 1.0 X-Mailer: Evolution 2.24.1 Content-Transfer-Encoding: 7bit X-Source-IP: acsmt703.oracle.com [141.146.40.81] X-Auth-Type: Internal IP X-CT-RefId: str=0001.0A090206.4966458A.0195:SCFSTAT928724,ss=1,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1434 Lines: 46 On Thu, 2009-01-08 at 10:16 -0800, Linus Torvalds wrote: > > On Thu, 8 Jan 2009, Steven Rostedt wrote: > > > > Ouch! I think you are on to something: > > Yeah, there's somethign there, but looking at Chris' backtrace, there's > nothing there to disable preemption. So if it was this simple case, it > should still have preempted him to let the other process run and finish > up. > My .config has no lockdep or schedule debugging and voluntary preempt. I do have CONFIG_INLINE_OPTIMIZE on, its a good name for trusting gcc I guess. > So I don't think Chris' softlockup is at least _exactly_ that case. > There's something else going on too. > > That said, I do think it's a mistake for us to care about the value of > "spin_on_owner()". I suspect v8 should > > - always have > > if (need_resched()) > break > > in the outer loop. > > - drop the return value from "spin_on_owner()", and just break out if > anything changes (including the need_resched() flag). > > - I'd also drop the "old_value < 0 &&" test, and just test the > list_empty() unconditionally. > I'll give the above a shot, and we can address the preempt + !owner in another rev -chris -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/