[Bug 759535] New: gst_clock_id_unschedule isnt thread safe

[GStreamer (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=759535

            Bug ID: 759535
           Summary: gst_clock_id_unschedule isnt thread safe
    Classification: Platform
           Product: GStreamer
           Version: 1.4.5
                OS: Windows
            Status: NEW
          Severity: major
          Priority: Normal
         Component: gstreamer (core)
          Assignee: gstreamer-bugs at lists.freedesktop.org
          Reporter: james at stev.org
        QA Contact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---

Created attachment 317489
  --> https://bugzilla.gnome.org/attachment.cgi?id=317489&action=edit
Test case for gst_clock_id_unschedule

When using gst_clock_new_periodic_id and gst_clock_id_unschedule the
documentation claims they are thread safe but it seems to be impossible to
disable a timer without the risk of a race which can cause the application to
core. I trace this down to the fact that the timer can be active after
gst_clock_id_unschedule has returned. Which would make the api non thread safe
to use.

I have attached a test case for this which will cause the valgrind invalid
memory reads below

==11520== Invalid read of size 8
==11520==    at 0x57016DF: __GI_mempcpy (memcpy.S:107)
==11520==    by 0x56EE53C: _IO_file_xsputn@@GLIBC_2.2.5 (fileops.c:1312)
==11520==    by 0x56C0AB4: vfprintf (vfprintf.c:1642)
==11520==    by 0x56C9588: printf (printf.c:33)
==11520==    by 0x400B31: callback (in /home/james/tmp/a.out)
==11520==    by 0x4EC5421: gst_system_clock_async_thread (in
/usr/lib/x86_64-linux-gnu/libgstreamer-1.0.so.0.403.0)
==11520==    by 0x51B8924: g_thread_proxy (in
/lib/x86_64-linux-gnu/libglib-2.0.so.0.4200.1)
==11520==    by 0x545F0A4: start_thread (pthread_create.c:309)
==11520==    by 0x576ECFC: clone (clone.S:111)
==11520==  Address 0x6e574c3 is 3 bytes inside a block of size 12 free'd
==11520==    at 0x4C2BE10: free (in
/usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==11520==    by 0x400BF8: main (in /home/james/tmp/a.out)
==11520==

the test program can be compiled with  gcc -Wall gstclock.c `pkg-config
--cflags --libs gstreamer-1.0` on ubuntu

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