Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752956AbbDFRcR (ORCPT ); Mon, 6 Apr 2015 13:32:17 -0400 Received: from mail-ie0-f169.google.com ([209.85.223.169]:32964 "EHLO mail-ie0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751331AbbDFRcO (ORCPT ); Mon, 6 Apr 2015 13:32:14 -0400 MIME-Version: 1.0 In-Reply-To: <5522BB49.5060704@canonical.com> References: <20150331222327.GA12512@canonical.com> <20150401124336.GB12841@gmail.com> <20150401161047.GD12730@canonical.com> <551C6A48.9060805@canonical.com> <20150402182607.GA8896@gmail.com> <551D8FAF.5070805@canonical.com> <20150402190725.GA10570@gmail.com> <551DB0E2.1020607@canonical.com> <20150403054320.GA9863@gmail.com> <5522BB49.5060704@canonical.com> Date: Mon, 6 Apr 2015 10:32:14 -0700 X-Google-Sender-Auth: Ea7__-hBweQ5HZ428CX0kR65pTQ Message-ID: Subject: Re: [PATCH] smp/call: Detect stuck CSD locks From: Linus Torvalds To: Chris J Arges Cc: Ingo Molnar , Rafael David Tinoco , Peter Anvin , Jiang Liu , Peter Zijlstra , LKML , Jens Axboe , Frederic Weisbecker , Gema Gomez , "the arch/x86 maintainers" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1316 Lines: 28 On Mon, Apr 6, 2015 at 9:58 AM, Chris J Arges wrote: > > I noticed that with this patch it never reached 'csd: Detected > non-responsive CSD lock...' because it seems that ts_delta never reached > CSD_LOCK_TIMEOUT. I tried adjusting the TIMEOUT value and still got a > hang without reaching this statement. I made the ts0,ts1 values global > and put a counter into the while loop and found that the loop iterated > about 670 million times before the softlockup was detected. In addition > ts0 and ts1 both had the same values upon soft lockup, and thus would > never trip the CSD_LOCK_TIMEOUT check. Sounds like jiffies stops updating. Which doesn't sound unreasonable for when there is some IPI problem. How about just changing the debug patch to count iterations, and print out a warning when it reaches ten million or so. No, that's not the right thing to do in general, but for debugging this particular issue it's a quick hack that might just work. It's not like re-sending the IPI is "wrong" anyway. Linus -- 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/