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From: Namhyung Kim <namhyung@kernel.org>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@kernel.org>,
        Namhyung Kim <namhyung.kim@lge.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        David Ahern <dsahern@gmail.com>, Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH 09/14] perf ftrace: Add 'record' sub-command
References: <1366705872-12132-1-git-send-email-namhyung@kernel.org>
	<1366705872-12132-10-git-send-email-namhyung@kernel.org>
	<20130424141241.GG971@krava.brq.redhat.com>
Date: Thu, 25 Apr 2013 15:24:18 +0900
In-Reply-To: <20130424141241.GG971@krava.brq.redhat.com> (Jiri Olsa's message
	of "Wed, 24 Apr 2013 16:12:41 +0200")
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On Wed, 24 Apr 2013 16:12:41 +0200, Jiri Olsa wrote:
> I got following lockup for record command:
>
>   # ./perf --no-pager ftrace record ls
>   ...
>   hangs
>
>   in other terminal:
>
>   # pstack 14237
>   Thread 2 (Thread 0x7f3f1aa1d700 (LWP 14241)):
>   #0  0x0000003cec20b595 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
>   #1  0x0000000000446ebe in record_ftrace_raw_buffer (arg=0x21f9ce0) at builtin-ftrace.c:451
>   #2  0x0000003cec207d14 in start_thread () from /lib64/libpthread.so.0
>   #3  0x0000003cebaf168d in clone () from /lib64/libc.so.6
>   Thread 1 (Thread 0x7f3f1ba209c0 (LWP 14237)):
>   #0  0x0000003cec208e60 in pthread_join () from /lib64/libpthread.so.0
>   #1  0x0000000000449c8c in do_ftrace_record (ftrace=ftrace@entry=0x7fff1377d240) at builtin-ftrace.c:682
>   #2  0x000000000044a57b in __cmd_ftrace_record (argv=0x7fff1377d818, argc=<optimized out>, ftrace=0x7fff1377d240) at builtin-ftrace.c:1535
>   #3  cmd_ftrace (argc=2, argv=0x7fff1377d818, prefix=<optimized out>) at builtin-ftrace.c:1655
>   #4  0x000000000041a763 in run_builtin (p=p@entry=0x7d58a0, argc=argc@entry=3, argv=argv@entry=0x7fff1377d818) at perf.c:320
>   #5  0x0000000000419faf in handle_internal_command (argv=0x7fff1377d818, argc=3) at perf.c:377
>   #6  run_argv (argv=0x7fff1377d600, argcp=0x7fff1377d60c) at perf.c:421
>   #7  main (argc=3, argv=0x7fff1377d818) at perf.c:522
>

How often can you reproduce it?  I can't. :(

But it looks there's a race between cond_wait() and cond_broatcast().
I'll take a look at that.

Thanks for the test and the report,
Namhyung
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