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 27EADEB64DA for ; Wed, 28 Jun 2023 10:36:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230115AbjF1Kgn (ORCPT ); Wed, 28 Jun 2023 06:36:43 -0400 Received: from foss.arm.com ([217.140.110.172]:53442 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232430AbjF1Keb (ORCPT ); Wed, 28 Jun 2023 06:34:31 -0400 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 9D4A7C14; Wed, 28 Jun 2023 03:35:14 -0700 (PDT) Received: from [10.57.27.176] (unknown [10.57.27.176]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 84DD03F663; Wed, 28 Jun 2023 03:34:28 -0700 (PDT) Message-ID: Date: Wed, 28 Jun 2023 11:34:26 +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: Ian Rogers , Namhyung Kim Cc: 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-kernel@vger.kernel.org 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? > > Thanks, > Ian > >> Thanks, >> Namhyung