linux-kernel - Re: [PATCH] perf tool: Fix output unexpected messages in quiet mode

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Date:   Mon, 19 Dec 2022 17:28:00 +0800
From:   Yang Jihong <yangjihong1@...wei.com>
To:     Adrian Hunter <adrian.hunter@...el.com>, <peterz@...radead.org>,
        <mingo@...hat.com>, <acme@...nel.org>, <mark.rutland@....com>,
        <alexander.shishkin@...ux.intel.com>, <jolsa@...nel.org>,
        <namhyung@...nel.org>, <irogers@...gle.com>,
        <kan.liang@...ux.intel.com>, <kim.phillips@....com>,
        <german.gomez@....com>, <ravi.bangoria@....com>,
        <linux-perf-users@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] perf tool: Fix output unexpected messages in quiet mode

Hello,

On 2022/12/19 14:59, Adrian Hunter wrote:
> On 19/12/22 04:49, Yang Jihong wrote:
>> When perf uses quiet mode, perf_quiet_option sets debug_peo_args to -1,
> 
> Seems like redirect_to_stderr has similar issue?
The redirect_to_stderr is used only in the veprintf function:

   int veprintf(int level, int var, const char *fmt, va_list args)
   {
           int ret = 0;

           if (var >= level) {
                   if (use_browser >= 1 && redirect_to_stderr <= 0) {
                           ui_helpline__vshow(fmt, args);
                   } else {
                           ret = fprintf_time(debug_file);
                           ret += vfprintf(debug_file, fmt, args);
                   }
           }

           return ret;
   }

If use quiet mode, verbose sets to -1. (also assigned in the 
perf_quiet_option function)
Because "var >= level" is false, veprintf function returns directly, 
which avoids this problem.

However, there are cases where:
   # perf --debug stderr=-1 report -vvv 2>/tmp/debug

If stderr is -1, should we redirect pr_debug in this case?

Because I'm not sure if this is a problem,
if redirect_to_stderr needs to be fixed as well,
let me know and I'll submit a patch to fix it.

> 
>> and display_attr incorrectly determines the value of debug_peo_args.
>> As a result, unexpected information is displayed.
>>
>> Before:
>>    # perf record --quiet -- ls > /dev/null
>>    ------------------------------------------------------------
>>    perf_event_attr:
>>      size                             128
>>      { sample_period, sample_freq }   4000
>>      sample_type                      IP|TID|TIME|PERIOD
>>      read_format                      ID|LOST
>>      disabled                         1
>>      inherit                          1
>>      mmap                             1
>>      comm                             1
>>      freq                             1
>>      enable_on_exec                   1
>>      task                             1
>>      precise_ip                       3
>>      sample_id_all                    1
>>      exclude_guest                    1
>>      mmap2                            1
>>      comm_exec                        1
>>      ksymbol                          1
>>      bpf_event                        1
>>    ------------------------------------------------------------
>>    ...
>>
>> After:
>>    # perf record --quiet -- ls > /dev/null
>>    #
>>
>> Fixes: ccd26741f5e6 ("perf tool: Provide an option to print perf_event_open args and return value")
>> Signed-off-by: Yang Jihong <yangjihong1@...wei.com>
> 
> Reviewed-by: Adrian Hunter <adrian.hunter@...el.com>
> 
Thanks for reviewed-by.

Thanks,
Yang