[Bug 796731] New: gstplayer join to self cause deadlock

[GStreamer (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=796731

            Bug ID: 796731
           Summary: gstplayer join to self cause deadlock
    Classification: Platform
           Product: GStreamer
           Version: git master
                OS: other
            Status: NEW
          Severity: normal
          Priority: Normal
         Component: gst-plugins-bad
          Assignee: gstreamer-bugs at lists.freedesktop.org
          Reporter: rlandjon at gmail.com
        QA Contact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---

Based on gstplayer of app on Android, when we play/exit repeatedly, there may
be crash(an "error 'Resource deadlock would occur' ")

---
07-02 09:51:49.876 21512 21512 F DEBUG   : ABI: 'arm'
07-02 09:51:49.876 21512 21512 F DEBUG   : pid: 20491, tid: 21488, name:
GstPlayer
07-02 09:51:49.876 21512 21512 F DEBUG   : signal 5 (SIGTRAP), code -6
(SI_TKILL), fault addr --------
07-02 09:51:49.876 21512 21512 F DEBUG   :     r0 00000000  r1 000053f0  r2
00000005  r3 ffffffff
07-02 09:51:49.876 21512 21512 F DEBUG   :     r4 ffffffff  r5 00000006  r6
ec2774cc  r7 0000010c
07-02 09:51:49.876 21512 21512 F DEBUG   :     r8 e7ad0400  r9 ec2774cc  sl
ed12b068  fp 00000000
07-02 09:51:49.876 21512 21512 F DEBUG   :     ip 00000004  sp e53ff6a8  lr
ebf65523  pc ee5afa94  cpsr 00010010
07-02 09:51:49.884 21512 21512 F DEBUG   : 
07-02 09:51:49.884 21512 21512 F DEBUG   : backtrace:
07-02 09:51:49.884 21512 21512 F DEBUG   :     #00 pc 0004aa94 
/system/lib/libc.so (tgkill+12)
07-02 09:51:49.884 21512 21512 F DEBUG   :     #01 pc 014b951f 
/system/lib/libgstreamer_android.so (g_log_default_handler+86)
07-02 09:51:49.884 21512 21512 F DEBUG   :     #02 pc 014b9705 
/system/lib/libgstreamer_android.so (g_logv+456)
07-02 09:51:49.884 21512 21512 F DEBUG   :     #03 pc 014b97ad 
/system/lib/libgstreamer_android.so (g_log+12)
07-02 09:51:49.884 21512 21512 F DEBUG   :     #04 pc 014dc37d 
/system/lib/libgstreamer_android.so
07-02 09:51:49.884 21512 21512 F DEBUG   :     #05 pc 014cb0e9 
/system/lib/libgstreamer_android.so (g_thread_join+52)
07-02 09:51:49.884 21512 21512 F DEBUG   :     #06 pc 00014745 
/system/lib/libmmpadapter.so
07-02 09:51:49.884 21512 21512 F DEBUG   :     #07 pc 01484cd1 
/system/lib/libgstreamer_android.so (g_object_unref+212)
07-02 09:51:49.884 21512 21512 F DEBUG   :     #08 pc 000122ad 
/system/lib/libmmpadapter.so
07-02 09:51:49.884 21512 21512 F DEBUG   :     #09 pc 00017cc7 
/system/lib/libmmpadapter.so
07-02 09:51:49.884 21512 21512 F DEBUG   :     #10 pc 000183cb 
/system/lib/libmmpadapter.so
07-02 09:51:49.884 21512 21512 F DEBUG   :     #11 pc 000185c9 
/system/lib/libmmpadapter.so
07-02 09:51:49.884 21512 21512 F DEBUG   :     #12 pc 014b57ff 
/system/lib/libgstreamer_android.so (g_main_context_dispatch+206)
07-02 09:51:49.884 21512 21512 F DEBUG   :     #13 pc 014b59a1 
/system/lib/libgstreamer_android.so
07-02 09:51:49.884 21512 21512 F DEBUG   :     #14 pc 014b5c49 
/system/lib/libgstreamer_android.so (g_main_loop_run+204)
07-02 09:51:49.884 21512 21512 F DEBUG   :     #15 pc 000180ad 
/system/lib/libmmpadapter.so
07-02 09:51:49.885 21512 21512 F DEBUG   :     #16 pc 014cad8d 
/system/lib/libgstreamer_android.so
07-02 09:51:49.885 21512 21512 F DEBUG   :     #17 pc 00047db7 
/system/lib/libc.so (_ZL15__pthread_startPv+22)
07-02 09:51:49.885 21512 21512 F DEBUG   :     #18 pc 0001af7f 
/system/lib/libc.so (__start_thread+32)


Add a line log tells us that sometimes we might call a join on the same thread,
----
static void
gst_player_dispose (GObject * object)
{
  GstPlayer *self = GST_PLAYER (object);

  GST_TRACE_OBJECT (self, "Stopping main thread");
  *if (self->thread == g_thread_self()) 
  *   __android_log_print(ANDROID_LOG_DEBUG, "####", "Oooops,you cannot join to
yourself!!!!");
   ...
     if (self->loop) {
      g_main_loop_quit (self->loop);
      g_thread_join(self->thread);
   ...
  }

You cannot join to yourself. The POSIX manpage for pthread_join
specifies(http://pubs.opengroup.org/onlinepubs/7908799/xsh/pthread_join.html)
that you may get a deadlock error,

So we call change_state (self, GST_PLAYER_STATE_STOPPED) in gst_player_main,
which gives the cleanup function state_changed_signal_data_free the opportunity
to unref GstPlayer in the self->thread thread, causing the above error,we need
to think about it carefully :(

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