Since locking was added to kdenlive/filter_freeze.c (commit b698c58e57643e9df6941d91b07a40c997bd7e64), it now deadlocks.
A simple mlt xml file is attached that reproduces the problem. filter_freeze is recursively locking it's filter service mutex, and so the second lock blocks forever. The deadlocked stack trace is below. filter_freeze filter_get_image() locks the mutex, then calls mlt_frame_get_image() on the freeze_frame it got from the producer, which calls into filter_freeze filter_get_image() again which attempts to relock the mutex and deadlocks. It seems like the problem is when filter_freeze gets the frame from its producer, it is getting the filtered frame instead of the raw frame from the producer because mlt_service_get_frame() applies filters. Should filter_freeze be getting the freeze_frame directly from the producer, unfiltered, by calling producer->get_frame() directly instead of mlt_service_get_frame()? But it seems like we would want other filters to apply, just not filter_freeze itself. Or maybe just allow mutexes to be recursively locked (initialize them with PTHREAD_MUTEX_RECURSIVE)? #0 0x00007ffff79a3464 in __lll_lock_wait () from /lib/libpthread.so.0 #1 0x00007ffff799e5d9 in _L_lock_953 () from /lib/libpthread.so.0 #2 0x00007ffff799e3fb in pthread_mutex_lock () from /lib/libpthread.so.0 #3 0x00007ffff7bc4db5 in mlt_service_lock (self=0x6cf120) at mlt_service.c:137 #4 0x00007fffefeb73ee in filter_get_image (this=0x6dcd50, image=0x7fffffffdb98, format=0x7fffffffdf0c, width=0x7fffffffdf08, height=0x7fffffffdf04, writable=1) at filter_freeze.c:53 #5 0x00007ffff7bbc4c9 in mlt_frame_get_image (self=0x6dcd50, buffer=0x7fffffffdb98, format=0x7fffffffdf0c, width=0x7fffffffdf08, height=0x7fffffffdf04, writable=1) at mlt_frame.c:453 #6 0x00007fffefeb7601 in filter_get_image (this=0x6d7fe0, image=0x7fffffffdef0, format=0x7fffffffdf0c, width=0x7fffffffdf08, height=0x7fffffffdf04, writable=0) at filter_freeze.c:77 #7 0x00007ffff7bbc4c9 in mlt_frame_get_image (self=0x6d7fe0, buffer=0x7fffffffdef0, format=0x7fffffffdf0c, width=0x7fffffffdf08, height=0x7fffffffdf04, writable=0) at mlt_frame.c:453 #8 0x00007ffff7bd0d68 in producer_get_image (self=0x68adb0, buffer=0x7fffffffdef0, format=0x7fffffffdf0c, width=0x7fffffffdf08, height=0x7fffffffdf04, writable=0) at mlt_tractor.c:275 [...] Hmm, actually a workaround seems to be to set in="1" on the freeze filter - so since we are freezing frame 0 that frame is then not filtered through freeze again. Andrew
simple-deadlock.mlt
Description: Binary data
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