From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933480AbcBCHJT (ORCPT ); Wed, 3 Feb 2016 02:09:19 -0500 Received: from mga11.intel.com ([192.55.52.93]:38567 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933155AbcBCHJR (ORCPT ); Wed, 3 Feb 2016 02:09:17 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.22,388,1449561600"; d="scan'208";a="739636270" Subject: Re: [PATCH 2/2] perf tools: Fix fault in error patch of intel_pt_process_auxtrace_info() To: Arnaldo Carvalho de Melo References: <1454346792-24419-1-git-send-email-acme@kernel.org> <1454346792-24419-3-git-send-email-acme@kernel.org> <56B083D3.2000402@intel.com> <20160202155225.GD32488@kernel.org> Cc: Wang Nan , Ingo Molnar , linux-kernel@vger.kernel.org, Wang Nan , Josh Poimboeuf From: Adrian Hunter Message-ID: <56B1A79A.6040703@intel.com> Date: Wed, 3 Feb 2016 09:09:14 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0 MIME-Version: 1.0 In-Reply-To: <20160202155225.GD32488@kernel.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/02/2016 5:52 p.m., Arnaldo Carvalho de Melo wrote: > Em Tue, Feb 02, 2016 at 12:24:19PM +0200, Adrian Hunter escreveu: >> This patch does not fix the problem because the thread__zput() will still >> segfault later if the error path is not taken. >> >> Sorry, I didn't look closely at this patch because I was not expecting it >> to be taken because of the fix I had already sent: >> >> http://marc.info/?l=linux-kernel&m=145431692623940 >> >> However if you want to keep the struct thread rbtree / list union, the >> simple fix would be to reinstate the list initialization in this particular >> case i.e.: > > So, can I go with the following patch+description+authorship? Fine by me. Thank you! > > From 3a4acda1ecbd290973de08250d7dcdfaf5b2fe0f Mon Sep 17 00:00:00 2001 > From: Adrian Hunter > Date: Mon, 1 Feb 2016 03:21:04 +0000 > Subject: [PATCH 1/1] perf tools: Fix thread lifetime related segfaut in intel_pt > > intel_pt_process_auxtrace_info() creates a pt->unknown_thread thread > that eventually needs to be freed by the last thread__put() on it, when > its refcount hits zero, which may happen in > intel_pt_process_auxtrace_info() error handling path and triggers the > following segfault, which would happen as well at intel_pt_free, when > tools using this intel_pt codebase frees up resources: > > # perf record -I -e intel_pt/tsc=1,noretcomp=1/u /bin/ls > 0 a anaconda-ks.cfg bin perf.data perf.data.old perf-f23-bringup.todo > [ perf record: Woken up 1 times to write data ] > [ perf record: Captured and wrote 0.217 MB perf.data ] > # > # perf script -F event,comm,pid,tid,time,addr,ip,sym,dso,iregs > Samples for 'instructions:u' event do not have IREGS attribute set. Cannot print 'iregs' field. > intel_pt_synth_events: failed to synthesize 'instructions' event type > Segmentation fault (core dumped) > # > > The problem is: there's a union in 'struct thread' combines a list_head > and a rb_node. The standard life cycle of a thread is: init rb_node in > the constructor, insert it into machine->threads rbtree using rb_node, > move it to machine->dead_threads using list_head, clean in the last > thread__put: list_del_init(&thread->node). > > In the above command, it clean a thread before adding it into list, > causes the above segfault. > > Since pt->unknown_thread will never live in an rbtree, initialize its > list node so that when list_del_init() is done on it we don't segfault. > > After this patch: > > # perf script -F event,comm,pid,tid,time,addr,ip,sym,dso,iregs > Samples for 'instructions:u' event do not have IREGS attribute set. Cannot print 'iregs' field. > intel_pt_synth_events: failed to synthesize 'instructions' event type > 0x248 [0x88]: failed to process type: 70 > # > > Reported-by: Tong Zhang > Reported-by: Wang Nan > Signed-off-by: Adrian Hunter > Tested-by: Arnaldo Carvalho de Melo > Cc: Josh Poimboeuf > Link: http://lkml.kernel.org/r/1454296865-19749-1-git-send-email-wangnan0@huawei.com > Signed-off-by: Arnaldo Carvalho de Melo > --- > tools/perf/util/intel-pt.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c > index 81a2eb77ba7f..05d815851be1 100644 > --- a/tools/perf/util/intel-pt.c > +++ b/tools/perf/util/intel-pt.c > @@ -2068,6 +2068,15 @@ int intel_pt_process_auxtrace_info(union perf_event *event, > err = -ENOMEM; > goto err_free_queues; > } > + > + /* > + * Since this thread will not be kept in any rbtree not in a > + * list, initialize its list node so that at thread__put() the > + * current thread lifetime assuption is kept and we don't segfault > + * at list_del_init(). > + */ > + INIT_LIST_HEAD(&pt->unknown_thread->node); > + > err = thread__set_comm(pt->unknown_thread, "unknown", 0); > if (err) > goto err_delete_thread; >