[gstreamer-bugs] [Bug 577671] New: [rtspsrc] deadlock on shutdown (locking order problem?)

[GStreamer (bugzilla.gnome.org)]

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  GStreamer | gst-plugins-good | Ver: git
           Summary: [rtspsrc] deadlock on shutdown (locking order problem?)
           Product: GStreamer
           Version: git
          Platform: Other
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-plugins-good
        AssignedTo: gstreamer-bugs at lists.sourceforge.net
        ReportedBy: t.i.m at zen.co.uk
         QAContact: gstreamer-bugs at lists.sourceforge.net
     GNOME version: Unspecified
   GNOME milestone: Unspecified


Running the test program from bug #577318 I quickly get deadlocks like this:

(gdb) thread apply all bt

Thread 8 (Thread 0xb48deb90 (LWP 22492)):
#0  0xb80d3422 in __kernel_vsyscall ()
#1  0xb7d67075 in pthread_cond_wait@@GLIBC_2.3.2 () from
/lib/tls/i686/cmov/libpthread.so.0
#2  0xb806c09b in gst_system_clock_async_thread (clock=0x9f2c000) at
gstsystemclock.c:385
#3  0xb7dda02f in g_thread_create_proxy (data=0x9f209d0) at
/build/buildd/glib2.0-2.18.2/glib/gthread.c:635
#4  0xb7d6350f in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#5  0xb7ce0a0e in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 6 (Thread 0xb58e0b90 (LWP 22490)):
#0  0xb80d3422 in __kernel_vsyscall ()
#1  0xb7d69d09 in __lll_lock_wait () from /lib/tls/i686/cmov/libpthread.so.0
#2  0xb7d65114 in _L_lock_89 () from /lib/tls/i686/cmov/libpthread.so.0
#3  0xb7d64a42 in pthread_mutex_lock () from /lib/tls/i686/cmov/libpthread.so.0
#4  0xb7dd9f73 in IA__g_static_rec_mutex_lock (mutex=0x9e7d7f8) at
/build/buildd/glib2.0-2.18.2/glib/gthread.c:313
#5  0xb7a92fba in gst_rtspsrc_loop (src=0x9f0e240) at gstrtspsrc.c:2773
#6  0xb80719e3 in gst_task_func (task=0x9f571e0, tclass=0x9e142c0) at
gsttask.c:192
#7  0xb7ddb6c6 in g_thread_pool_thread_proxy (data=0x9e14350) at
/build/buildd/glib2.0-2.18.2/glib/gthreadpool.c:265
#8  0xb7dda02f in g_thread_create_proxy (data=0x9f49170) at
/build/buildd/glib2.0-2.18.2/glib/gthread.c:635
#9  0xb7d6350f in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#10 0xb7ce0a0e in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 1 (Thread 0xb7bbd8c0 (LWP 22482)):
#0  0xb80d3422 in __kernel_vsyscall ()
#1  0xb7d69d09 in __lll_lock_wait () from /lib/tls/i686/cmov/libpthread.so.0
#2  0xb7d65114 in _L_lock_89 () from /lib/tls/i686/cmov/libpthread.so.0
#3  0xb7d64a42 in pthread_mutex_lock () from /lib/tls/i686/cmov/libpthread.so.0
#4  0xb7dd9f73 in IA__g_static_rec_mutex_lock (mutex=0x9f14bb0) at
/build/buildd/glib2.0-2.18.2/glib/gthread.c:313
#5  0xb7a8e362 in gst_rtspsrc_close (src=0x9f0e240) at gstrtspsrc.c:4655
#6  0xb7a910e0 in gst_rtspsrc_change_state (element=0x9f0e240,
transition=GST_STATE_CHANGE_PAUSED_TO_READY) at gstrtspsrc.c:5192
#7  0xb8033f78 in gst_element_change_state (element=0x9f0e240,
transition=GST_STATE_CHANGE_PAUSED_TO_READY) at gstelement.c:2430
#8  0xb8036ebc in gst_element_set_state_func (element=0x9f0e240,
state=GST_STATE_READY) at gstelement.c:2380
#9  0xb80331b2 in gst_element_set_state (element=0x9f0e240,
state=GST_STATE_READY) at gstelement.c:2283
#10 0xb8024e8f in gst_bin_change_state_func (element=0x9f075a0,
transition=GST_STATE_CHANGE_PAUSED_TO_READY) at gstbin.c:2062
#11 0xb80574ba in gst_pipeline_change_state (element=0x9f075a0,
transition=GST_STATE_CHANGE_PAUSED_TO_READY) at gstpipeline.c:465
#12 0xb8033f78 in gst_element_change_state (element=0x9f075a0,
transition=GST_STATE_CHANGE_PAUSED_TO_READY) at gstelement.c:2430
#13 0xb8033d0e in gst_element_continue_state (element=0x9f075a0,
ret=GST_STATE_CHANGE_NO_PREROLL) at gstelement.c:2134
#14 0xb80342ab in gst_element_change_state (element=0x9f075a0,
transition=GST_STATE_CHANGE_PLAYING_TO_PAUSED) at gstelement.c:2474
#15 0xb8036ebc in gst_element_set_state_func (element=0x9f075a0,
state=GST_STATE_NULL) at gstelement.c:2380
#16 0xb80331b2 in gst_element_set_state (element=0x9f075a0,
state=GST_STATE_NULL) at gstelement.c:2283
#17 0x08048bdb in main ()

which looks like a locking order problem to me:

 - streaming thread takes STREAMING_LOCK in _loop()

 - application thread in gst_rtspsrc_close():
     - takes STATE_LOCK
     - does gst_task_stop()
     - takes STREAM_LOCK, waits for streaming thread to release it

 - streaming thread takes STATE_LOCK in _loop_interleaved(),
   waits for application thread to release it

Not 100% sure what the correct solution is at this point, so just filing a bug
for now.


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