linux-kernel - Re: [PATCH v3 0/2] perf: add support for logging debug messages to file

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Message-ID: <20191008123201.qk5yfeys4ahpjopp@mail.google.com>
Date:   Tue, 8 Oct 2019 20:32:02 +0800
From:   Changbin Du <changbin.du@...il.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Changbin Du <changbin.du@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/2] perf: add support for logging debug messages to
 file

On Mon, Oct 07, 2019 at 01:26:24PM +0200, Jiri Olsa wrote:
> On Fri, Oct 04, 2019 at 10:39:52AM +0800, Changbin Du wrote:
> > When in TUI mode, it is impossible to show all the debug messages to
> > console. This make it hard to debug perf issues using debug messages.
> > This patch adds support for logging debug messages to file to resolve
> > this problem.
> > 
> > v3:
> >   o fix a segfault issue.
> 
> heya,
> getting segfault for this:
> 
> [jolsa@...va perf]$ ./perf report -vv 2>out
> Segmentation fault (core dumped)
>
This can be fixed by below change. In this case, log_file is NULL.

--- a/tools/perf/util/debug.c
+++ b/tools/perf/util/debug.c
@@ -37,8 +37,10 @@ int veprintf(int level, int var, const char *fmt, va_list args)
        if (var >= level) {
                if (use_browser >= 1 && !log_file)
                        ui_helpline__vshow(fmt, args);
-               else
+               else if (log_file)
                        ret = vfprintf(log_file, fmt, args);
+               else
+                       ret = vfprintf(stderr, fmt, args);
        }
 
        return ret;



> jirka
> 
> > v2:
> >   o specific all debug options one time.
> > 
> > Changbin Du (2):
> >   perf: support multiple debug options separated by ','
> >   perf: add support for logging debug messages to file
> > 
> >  tools/perf/Documentation/perf.txt |  15 ++--
> >  tools/perf/util/debug.c           | 124 +++++++++++++++++++-----------
> >  2 files changed, 90 insertions(+), 49 deletions(-)
> > 
> > -- 
> > 2.20.1
> > 

-- 
Cheers,
Changbin Du