From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752090AbaF0RfA (ORCPT ); Fri, 27 Jun 2014 13:35:00 -0400 Received: from mail-wi0-f171.google.com ([209.85.212.171]:45398 "EHLO mail-wi0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751953AbaF0Re5 (ORCPT ); Fri, 27 Jun 2014 13:34:57 -0400 Message-ID: <1403890493.5830.33.camel@marge.simpson.net> Subject: Re: Filesystem lockup with CONFIG_PREEMPT_RT From: Mike Galbraith To: Steven Rostedt Cc: Austin Schuh , Thomas Gleixner , Richard Weinberger , LKML , rt-users Date: Fri, 27 Jun 2014 19:34:53 +0200 In-Reply-To: <20140627100157.6b0143a5@gandalf.local.home> References: <1403873856.5827.56.camel@marge.simpson.net> <20140627100157.6b0143a5@gandalf.local.home> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2014-06-27 at 10:01 -0400, Steven Rostedt wrote: > This seems like a lot of hacks. It is exactly that, lacking proper pooper-scooper, show rt kernel how to not step in it. > I'm wondering if it would work if we > just have the rt_spin_lock_slowlock not call schedule(), but call > __schedule() directly. I mean it would keep with the mainline paradigm > as spinlocks don't sleep there, and one going to sleep in the -rt > kernel is similar to it being preempted by a very long NMI. Problem being that we do sleep there, do need wakeup. I have a hack that turns them back into spinning locks, but it.. works too :) > Does a spin_lock going to sleep really need to do all the presched and > postsched work? It would be lovely if we didn't have to do any of that. On the IO bit, I haven't seen hard evidence that the spinlock bit is absolutely required (better not be, it doesn't guarantee anything), but the combined hack did kill IO deadlock of multiple filesystems. -Mike