From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 82F03EB64DD for ; Mon, 3 Jul 2023 08:18:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231337AbjGCIS5 (ORCPT ); Mon, 3 Jul 2023 04:18:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57886 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231403AbjGCIS4 (ORCPT ); Mon, 3 Jul 2023 04:18:56 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 9D949E5F; Mon, 3 Jul 2023 01:18:53 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id EE7CC1FB; Mon, 3 Jul 2023 01:19:35 -0700 (PDT) Received: from [192.168.1.3] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E52483F73F; Mon, 3 Jul 2023 01:18:50 -0700 (PDT) Message-ID: <3a0fff38-b364-a6b4-1d10-41311e2073b4@arm.com> Date: Mon, 3 Jul 2023 09:18:50 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH 2/2] perf report: Don't add to histogram when there is no thread found Content-Language: en-US To: Namhyung Kim Cc: Ian Rogers , linux-perf-users@vger.kernel.org, Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Adrian Hunter , Suzuki K Poulose , Mike Leach , Leo Yan , John Garry , Will Deacon , linux-kernel@vger.kernel.org, coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org References: <20230626161059.324046-1-james.clark@arm.com> <20230626161059.324046-3-james.clark@arm.com> From: James Clark In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-perf-users@vger.kernel.org On 30/06/2023 22:02, Namhyung Kim wrote: > On Wed, Jun 28, 2023 at 1:06 PM Namhyung Kim wrote: >> >> On Wed, Jun 28, 2023 at 3:34 AM James Clark wrote: >>> >>> >>> >>> On 27/06/2023 18:19, Ian Rogers wrote: >>>> On Tue, Jun 27, 2023 at 9:58 AM Namhyung Kim wrote: >>>>> >>>>> On Tue, Jun 27, 2023 at 9:43 AM Ian Rogers wrote: >>>>>> >>>>>> On Mon, Jun 26, 2023 at 5:02 PM Namhyung Kim wrote: >>>>>>> >>>>>>> On Mon, Jun 26, 2023 at 05:10:58PM +0100, James Clark wrote: >>>>>>>> thread__find_map() chooses to exit without assigning a thread to the >>>>>>>> addr_location in some scenarios, for example when there are samples from >>>>>>>> a guest and perf_guest == false. This results in a segfault when adding >>>>>>>> to the histogram because it uses unguarded accesses to the thread member >>>>>>>> of the addr_location. >>>>>>> >>>>>>> Looking at the commit 0dd5041c9a0ea ("perf addr_location: Add >>>>>>> init/exit/copy functions") that introduced the change, I'm not sure if >>>>>>> it's the intend behavior. >>>>>>> >>>>>>> It might change maps and map, but not thread. Then I think no reason >>>>>>> to not set the al->thread at the beginning. >>>>>>> >>>>>>> How about this? Ian? >>>>>>> (I guess we can get rid of the duplicate 'al->map = NULL' part) >>>>>> >>>>>> It seemed strange that we were failing to find a map (the function's >>>>>> purpose) but then populating the address_location. The change below >>>>>> brings back that somewhat odd behavior. I'm okay with reverting to the >>>>>> old behavior, clearly there were users relying on it. We should >>>>>> probably also copy maps and not just thread, as that was the previous >>>>>> behavior. >>>>> >>>>> Probably. But it used to support samples without maps and I think >>>>> that's why it ignores the return value of thread__find_map(). So >>>>> we can expect al.map is NULL and maybe fine to leave it for now. >>>>> >>>>> As machine__resolve() returns -1 if it gets no thread, we should set >>>>> al.thread when it returns 0. >>>>> >>>>> Can I get your Acked-by? >>>> >>>> Yep: >>>> Acked-by: Ian Rogers >>> >>> Looks good to me too. Should I resend the set with this change instead >>> of my one? >> >> No, I can take care of that. I'll take this as your Acked-by. :) > > This part is applied to perf-tools-next, thanks! Thanks Namhyung