[Bug 797260] New: shmsink: do not render if element is unlocked

Mon Oct 8 20:55:36 UTC 2018

https://bugzilla.gnome.org/show_bug.cgi?id=797260

            Bug ID: 797260
           Summary: shmsink: do not render if element is unlocked
    Classification: Platform
           Product: GStreamer
           Version: 1.14.x
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: Normal
         Component: gst-plugins-bad
          Assignee: gstreamer-bugs at lists.freedesktop.org
          Reporter: aconchillo at gmail.com
        QA Contact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---

A race condition might occur in shmsink when wait-for-connecition is TRUE and
the pipeline is going to NULL.

The unlock() function will be called, but unlocking doesn't mean the render()
function can't be called again which in shmsink would could cause other locks
to happen (because of the conditional variable).

Since unlock() has already happened, the conditional variable will be waiting
and this will block the streaming thread not letting the pipeline to go to
NULL.

Thread 3 (Thread 0x7ff799ed2700 (LWP 30791)):
#0  syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38
#1  0x00007ff7a01e7eaf in g_cond_wait (cond=cond at entry=0x23008d8,
mutex=mutex at entry=0x2300608) at gthread-posix.c:1402
#2  0x00007ff79e6da4b5 in gst_shm_sink_render (bsink=0x23005f0,
buf=0x7ff78c00ab80) at gstshmsink.c:674
#3  0x00007ff79e919c23 in gst_base_sink_chain_unlocked
(basesink=basesink at entry=0x23005f0, obj=obj at entry=0x7ff78c00ab80,
is_list=is_list at entry=0, pad=<optimized out>) at gstbasesink.c:3546
#4  0x00007ff79e91b25c in gst_base_sink_chain_main (is_list=0,
obj=0x7ff78c00ab80, pad=<optimized out>, basesink=0x23005f0) at
gstbasesink.c:3672
#5  gst_base_sink_chain (pad=<optimized out>, parent=0x23005f0,
buf=0x7ff78c00ab80) at gstbasesink.c:3701
#6  0x00007ff7a074110b in gst_pad_chain_data_unchecked (data=<optimized out>,
type=4112, pad=0x22fc2f0) at gstpad.c:4322
#7  gst_pad_push_data (pad=pad at entry=0x22fc0a0, type=type at entry=4112,
data=<optimized out>, data at entry=0x7ff78c00ab80) at gstpad.c:4578
#8  0x00007ff7a0748bb3 in gst_pad_push (pad=pad at entry=0x22fc0a0,
buffer=0x7ff78c00ab80) at gstpad.c:4697
#9  0x00007ff79e91f98d in gst_base_src_loop (pad=0x22fc0a0) at
gstbasesrc.c:2957
#10 0x00007ff7a077b5b1 in gst_task_func (task=0x2305050) at gsttask.c:332
#11 0x00007ff7a01c51dc in g_thread_pool_thread_proxy (data=<optimized out>) at
gthreadpool.c:307
#12 0x00007ff7a01c4ac5 in g_thread_proxy (data=0x21e8720) at gthread.c:784
#13 0x00007ff79ff236ba in start_thread (arg=0x7ff799ed2700) at
pthread_create.c:333
#14 0x00007ff79fc5941d in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 2 (Thread 0x7ff79a6d3700 (LWP 30790)):
#0  0x00007ff79fc4d811 in __GI_ppoll (fds=0x7ff794001500, nfds=2,
timeout=<optimized out>, timeout at entry=0x0, sigmask=sigmask at entry=0x0) at
../sysdeps/unix/sysv/linux/ppoll.c:50
#1  0x00007ff7a0757a68 in ppoll (__ss=0x0, __timeout=0x0, __nfds=<optimized
out>, __fds=<optimized out>) at /usr/include/x86_64-linux-gnu/bits/poll2.h:77
#2  gst_poll_wait (set=0x21e8680, timeout=timeout at entry=18446744073709551615)
at gstpoll.c:1370
#3  0x00007ff79e6daff0 in pollthread_func (data=0x23005f0) at gstshmsink.c:830
#4  0x00007ff7a01c4ac5 in g_thread_proxy (data=0x21e86d0) at gthread.c:784
#5  0x00007ff79ff236ba in start_thread (arg=0x7ff79a6d3700) at
pthread_create.c:333
#6  0x00007ff79fc5941d in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 1 (Thread 0x7ff7a0e33700 (LWP 30789)):
#0  syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38
#1  0x00007ff7a01e70ac in g_mutex_lock_slowpath (mutex=mutex at entry=0x2300718)
at gthread-posix.c:1320
#2  0x00007ff7a01e7d52 in g_mutex_lock (mutex=mutex at entry=0x2300718) at
gthread-posix.c:1344
#3  0x00007ff79e913bcc in gst_base_sink_change_state (element=0x23005f0,
transition=GST_STATE_CHANGE_PLAYING_TO_PAUSED) at gstbasesink.c:5161
#4  0x00007ff7a072668e in gst_element_change_state
(element=element at entry=0x23005f0,
transition=transition at entry=GST_STATE_CHANGE_PLAYING_TO_PAUSED) at
gstelement.c:2952
#5  0x00007ff7a0726e07 in gst_element_set_state_func (element=0x23005f0,
state=GST_STATE_PAUSED) at gstelement.c:2906
#6  0x00007ff7a0702855 in gst_bin_element_set_state (next=GST_STATE_PAUSED,
current=GST_STATE_PLAYING, start_time=34130956, base_time=4159051704266325,
element=0x23005f0, bin=0x2302080) at gstbin.c:2604
#7  gst_bin_change_state_func (element=0x2302080,
transition=GST_STATE_CHANGE_PLAYING_TO_PAUSED) at gstbin.c:2946
#8  0x00007ff7a074e2ba in gst_pipeline_change_state (element=0x2302080,
transition=GST_STATE_CHANGE_PLAYING_TO_PAUSED) at gstpipeline.c:508
#9  0x00007ff7a072668e in gst_element_change_state
(element=element at entry=0x2302080,
transition=transition at entry=GST_STATE_CHANGE_PLAYING_TO_PAUSED) at
gstelement.c:2952
#10 0x00007ff7a0726e07 in gst_element_set_state_func (element=0x2302080,
state=GST_STATE_NULL) at gstelement.c:2906
#11 0x0000000000401e70 in test_shm_live (__i__=<optimized out>) at
elements/shm.c:218
#12 0x00007ff7a0a29c2e in tcase_run_tfun_fork (i=0, tfun=0x22e64d0,
tc=0x22e9b60, sr=0x22e6500) at check_run.c:465
#13 srunner_iterate_tcase_tfuns (tc=0x22e9b60, sr=0x22e6500) at check_run.c:237
#14 srunner_run_tcase (tc=0x22e9b60, sr=0x22e6500) at check_run.c:377
#15 srunner_iterate_suites (print_mode=CK_SILENT, exclude_tags=<optimized out>,
include_tags=<optimized out>, tcname=<optimized out>, sname=<optimized out>,
sr=0x22e6500) at check_run.c:205
#16 srunner_run_tagged (sr=sr at entry=0x22e6500, sname=<optimized out>,
sname at entry=0x0, tcname=<optimized out>, tcname at entry=0x0,
include_tags=<optimized out>, include_tags at entry=0x0, exclude_tags=<optimized
out>, exclude_tags at entry=0x0, print_mode=print_mode at entry=CK_NORMAL) at
check_run.c:740
#17 0x00007ff7a0a29d1d in srunner_run (sr=sr at entry=0x22e6500,
sname=sname at entry=0x0, tcname=tcname at entry=0x0,
print_mode=print_mode at entry=CK_NORMAL) at check_run.c:754
#18 0x00007ff7a0a29d2b in srunner_run_all (sr=sr at entry=0x22e6500,
print_mode=print_mode at entry=CK_NORMAL) at check_run.c:692
#19 0x00007ff7a0a1d8bd in gst_check_run_suite (suite=suite at entry=0x2140690,
name=name at entry=0x402ae5 "shm", fname=fname at entry=0x4029d8 "elements/shm.c") at
gstcheck.c:1067
#20 0x0000000000401aaf in main (argc=1, argv=0x7ffff45dcab8) at
elements/shm.c:249

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