From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alan Modra Subject: Re: [PATCH net-next] af_unix: fix a fatal race with bit fields Date: Fri, 3 May 2013 11:01:36 +0930 Message-ID: <20130503013136.GN5221@bubble.grove.modra.org> References: <1367370761.11020.22.camel@edumazet-glaptop> <20130501115103.58e40f37@kryten> <1367375060.11020.24.camel@edumazet-glaptop> <20130501035425.GD5221@bubble.grove.modra.org> <1367384672.11020.34.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Anton Blanchard , David Miller , netdev , linuxppc-dev@lists.ozlabs.org, Paul Mackerras , Ambrose Feinstein To: Eric Dumazet Return-path: Received: from mail-pa0-f51.google.com ([209.85.220.51]:36254 "EHLO mail-pa0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752505Ab3ECBbp (ORCPT ); Thu, 2 May 2013 21:31:45 -0400 Received: by mail-pa0-f51.google.com with SMTP id ld10so646003pab.24 for ; Thu, 02 May 2013 18:31:45 -0700 (PDT) Content-Disposition: inline In-Reply-To: <1367384672.11020.34.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, Apr 30, 2013 at 10:04:32PM -0700, Eric Dumazet wrote: > These kind of errors are pretty hard to find, its a pity to spend time > on them. Well, yes. From the first comment in gcc PR52080. "For the following testcase we generate a 8 byte RMW cycle on IA64 which causes locking problems in the linux kernel btrfs filesystem." Did someone fix btrfs, but not check other kernel locks? Having now hit the same problem again, have you checked that other kernel locks don't have adjacent bit fields in the same 64-bit word? And comment the struct to ensure someone doesn't optimize those unsigned chars back to bit fields. -- Alan Modra Australia Development Lab, IBM