Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753986Ab0H0Obr (ORCPT ); Fri, 27 Aug 2010 10:31:47 -0400 Received: from relay2.sgi.com ([192.48.179.30]:35212 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751872Ab0H0Obo (ORCPT ); Fri, 27 Aug 2010 10:31:44 -0400 Date: Fri, 27 Aug 2010 15:31:35 +0100 From: Hedi Berriche To: Petr Tesarik Cc: linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org, Tony Luck Subject: Re: Serious problem with ticket spinlocks on ia64 Message-ID: <20100827143135.GY18967@zorg.emea.sgi.com> Mail-Followup-To: Petr Tesarik , linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org, Tony Luck References: <201008271537.35709.ptesarik@suse.cz> <20100827134802.GX18967@zorg.emea.sgi.com> <201008271609.16099.ptesarik@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201008271609.16099.ptesarik@suse.cz> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1392 Lines: 38 On Fri, Aug 27, 2010 at 15:09 Petr Tesarik wrote: | On Friday 27 of August 2010 15:48:02 Hedi Berriche wrote: | | > One more fact, the problem was introduced by commit | > | > commit 9d40ee200a527ce08ab8c793ba8ae3e242edbb0e | > Author: Tony Luck | > Date: Wed Oct 7 10:54:19 2009 -0700 | > | > [IA64] Squeeze ticket locks back into 4 bytes. | > | > Reverting the patch makes the problem go away. | > | > IOW, and as far as testing shows, the first incarnation of the ticket locks | > implementation on IA64 (commit 2c8696), the one that used 8 bytes, does not | > exhibit this problem. | | I wouldn't be so sure about it. Given that I have only observed the problem | when the spinlock value wraps around, then an 8-byte spinlock might only need | much more time to trigger the bug. That's a possibility and that's why I said "as far as testing shows". That said, I'm letting my already over 36 hours run carry on chewing CPU time, and see if it will eventually trip the same problem seen with 4-byte ticket locks. Cheers, Hedi. -- Hedi Berriche Global Product Support http://www.sgi.com/support -- 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/