Re: [PATCH 09/14] perf ftrace: Add 'record' sub-command

[Jiri Olsa <jolsa@redhat.com>]

On Mon, May 06, 2013 at 10:44:56AM +0900, Namhyung Kim wrote:
> Hi Jiri,
> 
> Sorry for late reply.  I've been busy these days.
> 
> On Thu, 25 Apr 2013 15:24:18 +0900, Namhyung Kim wrote:
> > 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.
> 
> I think the problem is that a recorder can be blocked if it received a
> broadcast signal before calling cond_wait().  So I modified the code to
> place signaling ready_cond and waiting start_cond in the same cs.
> 
> Does the patch below fix your problem?

yes.. without the patch I get lockup in like 10 minutes
with the patch the test is now ok for almost an hour..

jirka