From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761071Ab3LIOF2 (ORCPT ); Mon, 9 Dec 2013 09:05:28 -0500 Received: from mail-pb0-f50.google.com ([209.85.160.50]:54914 "EHLO mail-pb0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760384Ab3LIOFZ (ORCPT ); Mon, 9 Dec 2013 09:05:25 -0500 Message-ID: <52A5CE1B.3030007@gmail.com> Date: Mon, 09 Dec 2013 07:05:15 -0700 From: David Ahern User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:24.0) Gecko/20100101 Thunderbird/24.1.1 MIME-Version: 1.0 To: Jiri Olsa CC: acme@ghostprotocols.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH] perf tool: Ensure forward progress unwinding frames References: <1385942509-11445-1-git-send-email-dsahern@gmail.com> <52A4B065.9080804@gmail.com> <20131209100205.GA1242@krava.brq.redhat.com> In-Reply-To: <20131209100205.GA1242@krava.brq.redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/9/13, 3:02 AM, Jiri Olsa wrote: >> On 12/1/13, 5:01 PM, David Ahern wrote: >>> The dwarf option for callstacks is getting stuck on the unwind and showing >>> repeated frames. For example, >>> >>> qemu-system-x86 13759 [001] 287663.084957: syscalls:sys_enter_futex: uaddr: 0x7f770a958700, op: 0x00000081, val: 0x00000001, utime: 0x7f75ea >>> 7f7705fd23ea __lll_unlock_wake (/lib64/libpthread-2.14.90.so) >>> 7f7705fcf045 _L_unlock_649 (/lib64/libpthread-2.14.90.so) >>> 7f7705fcf045 _L_unlock_649 (/lib64/libpthread-2.14.90.so) >>> 7f7705fcf045 _L_unlock_649 (/lib64/libpthread-2.14.90.so) >>> 7f7705fcf045 _L_unlock_649 (/lib64/libpthread-2.14.90.so) >>> 7f7705fcf045 _L_unlock_649 (/lib64/libpthread-2.14.90.so) >>> ... > > I wonder this is us or libunwind bug (or cfi code) ;-) > > looks like you can reproduce..? are you using the latest libunwind? $ rpm -q libunwind libunwind-0.99-2.20110424git1e10c293.fc16.x86_64 > > >>> (Last frame repeats 126 times) >>> >>> Catch that the same frame is hit multiple times and break out of the loop. >>> >>> With this patch: >>> >>> qemu-system-x86 13759 [001] 287663.084967: syscalls:sys_exit_futex: 0x1 >>> 7f7705fd23ea __lll_unlock_wake (/lib64/libpthread-2.14.90.so) >>> 7f7705fcf045 _L_unlock_649 (/lib64/libpthread-2.14.90.so) >>> >>> Signed-off-by: David Ahern >>> Cc: Jiri Olsa >>> --- >>> tools/perf/util/unwind.c | 5 +++++ >>> 1 file changed, 5 insertions(+) >>> >>> diff --git a/tools/perf/util/unwind.c b/tools/perf/util/unwind.c >>> index 0efd5393de85..817ffc1f3a00 100644 >>> --- a/tools/perf/util/unwind.c >>> +++ b/tools/perf/util/unwind.c >>> @@ -563,6 +563,7 @@ static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb, >>> { >>> unw_addr_space_t addr_space; >>> unw_cursor_t c; >>> + unw_word_t prev_ip = 0; >>> int ret; >>> >>> addr_space = unw_create_addr_space(&accessors, 0); >>> @@ -579,6 +580,10 @@ static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb, >>> unw_word_t ip; >>> >>> unw_get_reg(&c, UNW_REG_IP, &ip); >>> + if (ip == prev_ip) >>> + break; >>> + prev_ip = ip; > > hum, how about recursion? > > how about some counter and break after some insane value I chose > 1 as the insane value. Do you have a suggestion on something else? 5? 10? > and maybe display some warning.. > > qemu-system-x86 13759 [001] 287663.084967: syscalls:sys_exit_futex: 0x1 > 7f7705fd23ea __lll_unlock_wake (/lib64/libpthread-2.14.90.so) > 7f7705fcf045 _L_unlock_649 (/lib64/libpthread-2.14.90.so) > warning: unwind broken sure. David