linux-kernel - Re: [PATCH v2] perf stat: Introduce skippable evsels

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Date:   Thu, 20 Apr 2023 08:22:56 -0400
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ian Rogers <irogers@...gle.com>
Cc:     Stephane Eranian <eranian@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>,
        "Yasin, Ahmad" <ahmad.yasin@...el.com>,
        "Taylor, Perry" <perry.taylor@...el.com>,
        "Alt, Samantha" <samantha.alt@...el.com>,
        "Biggers, Caleb" <caleb.biggers@...el.com>,
        "Wang, Weilin" <weilin.wang@...el.com>,
        Edward <edward.baker@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Florian Fischer <florian.fischer@...q.space>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] perf stat: Introduce skippable evsels



On 2023-04-20 7:33 a.m., Arnaldo Carvalho de Melo wrote:
> Em Wed, Apr 19, 2023 at 09:51:20AM -0700, Ian Rogers escreveu:
>> On Wed, Apr 19, 2023 at 7:16 AM Liang, Kan <kan.liang@...ux.intel.com> wrote:
>>> For ADL/RPL platforms
>>> - Segmentation fault which I just found this morning.
>>> # ./perf stat true
>>> Segmentation fault (core dumped)
>  
>> This may also stem from the reference count checking work that Arnaldo
>> is currently merging. It is hard to test hybrid because it uses
>> non-generic code paths.
> 
> Hey, could you please try this under gdb and provide a backtrace? 

Here is the backtrace.

#0  get_group_fd (thread=0, cpu_map_idx=<optimized out>,
evsel=0x555556015af0) at util/evsel.c:1722
#1  evsel__open_cpu (evsel=<optimized out>, cpus=<optimized out>,
threads=<optimized out>,
    start_cpu_map_idx=<optimized out>, end_cpu_map_idx=<optimized out>)
at util/evsel.c:2105
#2  0x000055555561dd9e in __run_perf_stat (run_idx=<optimized out>,
argv=0x7fffffffe1d0, argc=1)
    at builtin-stat.c:734
#3  run_perf_stat (run_idx=<optimized out>, argv=0x7fffffffe1d0, argc=1)
at builtin-stat.c:949
#4  cmd_stat (argc=1, argv=0x7fffffffe1d0) at builtin-stat.c:2537
#5  0x00005555556b56a0 in run_builtin (p=p@...ry=0x555555f84450
<commands+336>, argc=argc@...ry=2,
    argv=argv@...ry=0x7fffffffe1d0) at perf.c:323
#6  0x00005555555fe2d9 in handle_internal_command (argv=0x7fffffffe1d0,
argc=2) at perf.c:377
#7  run_argv (argv=<synthetic pointer>, argcp=<synthetic pointer>) at
perf.c:421
#8  main (argc=2, argv=0x7fffffffe1d0) at perf.c:537

Thanks,
Kan

> It may
> indeed be related to this refcount checking work, there was a bug fixed
> by the ARM guys for cs-etm and I combed thru and fixed some other use
> before check for NULL cases, maybe one more slipped up.
> 
> Here I couldn't reproduce, but I don't have a Intel hybrid system, will
> check with an ARM, but unsure if it will exercise the same code paths...
> 
> - Arnaldo