From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 50133 invoked by alias); 26 May 2016 19:11:41 -0000 Mailing-List: contact gdb-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sourceware.org Received: (qmail 50078 invoked by uid 89); 26 May 2016 19:11:41 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.9 required=5.0 tests=BAYES_05,RP_MATCHES_RCVD,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy=regs, boards, returnexp, Firefly X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Thu, 26 May 2016 19:11:40 +0000 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D8037486A2; Thu, 26 May 2016 19:11:38 +0000 (UTC) Received: from [127.0.0.1] (ovpn01.gateway.prod.ext.ams2.redhat.com [10.39.146.11]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u4QJBbUQ017676; Thu, 26 May 2016 15:11:38 -0400 Subject: Re: Debugging return.exp on ARM To: Simon Marchi , gdb@sourceware.org References: <574712FC.5090409@ericsson.com> Cc: Yao Qi From: Pedro Alves Message-ID: Date: Thu, 26 May 2016 19:11:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.0 MIME-Version: 1.0 In-Reply-To: <574712FC.5090409@ericsson.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-SW-Source: 2016-05/txt/msg00021.txt.bz2 On 05/26/2016 04:15 PM, Simon Marchi wrote: > Given that we give the right input to the kernel, even in the cases that > fail, I assume that the problem must be something like wrong cache invalidation > or memory barrier/sequencing. > > I ran this test in a loop and got these results: > > ODroid XU-4: > 263 fails > 737 successes > > Firefly RK3288: > 336 fails > 163 success > > First, is anybody able to reproduce the problem on other boards? Then, does anybody > have an idea what could cause this? - I'd suspect something odd with caches / barriers too. Did you try sprinkling in memory barrier instructions, and see whether it makes a difference? - I'd also try "si" + "info regs" instead of "next" after the return, and see if a register with a bad value pops up always at some specific instruction. - I'd try to see if pinning the thread to a core makes a difference. - Might help to show the kernel version. Thanks, Pedro Alves