From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752923Ab2GQE2B (ORCPT ); Tue, 17 Jul 2012 00:28:01 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:5664 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750842Ab2GQE17 (ORCPT ); Tue, 17 Jul 2012 00:27:59 -0400 X-Authority-Analysis: v=2.0 cv=ZuBv2qHG c=1 sm=0 a=s5Htg7xnQOKvHEu9STBOug==:17 a=OpT9cpI26MMA:10 a=IEFAe7w0650A:10 a=5SG0PmZfjMsA:10 a=Q9fys5e9bTEA:10 a=meVymXHHAAAA:8 a=ayC55rCoAAAA:8 a=UejcNrzcuEgphWSHMR0A:9 a=PUjeQqilurYA:10 a=s5Htg7xnQOKvHEu9STBOug==:117 X-Cloudmark-Score: 0 X-Originating-IP: 72.230.195.127 Message-ID: <1342499278.24525.13.camel@gandalf.stny.rr.com> Subject: Re: 3.4.4-rt13: btrfs + xfstests 006 = BOOM.. and a bonus rt_mutex deadlock report for absolutely free! From: Steven Rostedt To: Mike Galbraith Cc: Chris Mason , "Chris L. Mason" , "linux-rt-users@vger.kernel.org" , LKML , linux-fsdevel , Thomas Gleixner Date: Tue, 17 Jul 2012 00:27:58 -0400 In-Reply-To: <1342498722.7353.37.camel@marge.simpson.net> References: <1342072060.7338.102.camel@marge.simpson.net> <20120713125043.GH30128@shiny> <1342260883.7368.30.camel@marge.simpson.net> <20120715175612.GF25961@shiny.int.fusionio.com> <1342404140.7659.27.camel@marge.simpson.net> <1342454547.5410.3.camel@gandalf.stny.rr.com> <1342455968.7659.93.camel@marge.simpson.net> <1342456567.7659.97.camel@marge.simpson.net> <1342458195.2783.5.camel@acer.local.home> <1342498722.7353.37.camel@marge.simpson.net> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.4.3-1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2012-07-17 at 06:18 +0200, Mike Galbraith wrote: > > > There's that too. But the issue I was talking about is with all trylock > > loops. As holding an rt-mutex now disables migration, if a high priority > > process preempts a task that holds the lock, and then the high prio task > > starts spinning waiting for that lock to release, the lower priority > > process will never get to run to release it. The cpu_chill() doesn't > > help. > > Hrm. I better go make a testcase, this one definitely wants pounding > through thick skull. Actually, I was mistaken. I forgot that we defined 'cpu_chill()' as msleep(1) on RT, which would keep a deadlock from happening. It doesn't explain the performance enhancement you get :-/ -- Steve