| Message ID | 20170718233440.81731-1-wtc@google.com |
|---|---|
| State | Accepted |
| Commit | 8c3b329da21a05a977b21d1a3ad3ed8ce72f997b |
| Headers | show |
I researched the history of the line in h264_slice.c that this patch deleted. That line was implicitly added in commit 4da2ac5c7a491b20be62ad19d77526e62aa57c69: http://git.videolan.org/gitweb.cgi/ffmpeg.git/?p=ffmpeg.git;a=patch;h=4da2ac5c7a491b20be62ad19d77526e62aa57c69 Although commit 4da2ac5c7a491b20be62ad19d77526e62aa57c69 didn't modify h264_slice.c, the copy_fields macro call in ff_h264_update_thread_context() would copy the new default_ref[] field of H264Context. The copying of default_ref[] was made explicit in commit 98456d4d69e0fdcc328bb9e684ae776f5bc824e1, which replaced the copy_fields macro with field-by-field copies. http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=98456d4d69e0fdcc328bb9e684ae776f5bc824e1 Commit 4da2ac5c7a491b20be62ad19d77526e62aa57c69 makes it clear that the default_ref[] field of H264Context is supposed to be initialized (to values from the associated H264SliceContext) in h264_initialise_ref_list(), so it should not be propagated from one decoding thread to the next. Wan-Teh Chang
Hi, On Tue, Jul 18, 2017 at 7:34 PM, Wan-Teh Chang <wtc-at-google.com@ffmpeg.org > wrote: > default_ref[] is unconditionally initialized in h264_initialise_ref_list() > (called from ff_h264_build_ref_list(), called from h264_slice_init()). > > This fixes the following tsan warning when running fate-h264: > > WARNING: ThreadSanitizer: data race (pid=31070) > Write of size 8 at 0x7bbc000082a8 by thread T1 (mutexes: write M1628): > #0 memcpy /work/release-test/final/llvm.src/projects/compiler-rt/lib/ > tsan/../sanitizer_common/sanitizer_common_interceptors.inc:655:5 > (ffmpeg+0x10de9d) > #1 h264_initialise_ref_list ffmpeg/libavcodec/h264_refs.c:214:29 > (ffmpeg+0x1186b3f) > #2 ff_h264_build_ref_list ffmpeg/libavcodec/h264_refs.c:306 > (ffmpeg+0x1186b3f) > #3 h264_slice_init ffmpeg/libavcodec/h264_slice.c:1900:11 > (ffmpeg+0x1191149) > [..] > Previous read of size 8 at 0x7bbc000082a8 by main thread (mutexes: > write M1630): > #0 memcpy /work/release-test/final/llvm.src/projects/compiler-rt/lib/ > tsan/../sanitizer_common/sanitizer_common_interceptors.inc:655:5 > (ffmpeg+0x10de9d) > #1 ff_h264_update_thread_context ffmpeg/libavcodec/h264_slice.c:411:5 > (ffmpeg+0x118b7dc) > > Signed-off-by: Wan-Teh Chang <wtc@google.com> > --- > libavcodec/h264_slice.c | 1 - > 1 file changed, 1 deletion(-) Pushed. Ronald
diff --git a/libavcodec/h264_slice.c b/libavcodec/h264_slice.c index 6deb08fe6d..2fb89b189d 100644 --- a/libavcodec/h264_slice.c +++ b/libavcodec/h264_slice.c @@ -408,7 +408,6 @@ int ff_h264_update_thread_context(AVCodecContext *dst, memcpy(&h->poc, &h1->poc, sizeof(h->poc)); - memcpy(h->default_ref, h1->default_ref, sizeof(h->default_ref)); memcpy(h->short_ref, h1->short_ref, sizeof(h->short_ref)); memcpy(h->long_ref, h1->long_ref, sizeof(h->long_ref)); memcpy(h->delayed_pic, h1->delayed_pic, sizeof(h->delayed_pic));
default_ref[] is unconditionally initialized in h264_initialise_ref_list() (called from ff_h264_build_ref_list(), called from h264_slice_init()). This fixes the following tsan warning when running fate-h264: WARNING: ThreadSanitizer: data race (pid=31070) Write of size 8 at 0x7bbc000082a8 by thread T1 (mutexes: write M1628): #0 memcpy /work/release-test/final/llvm.src/projects/compiler-rt/lib/tsan/../sanitizer_common/sanitizer_common_interceptors.inc:655:5 (ffmpeg+0x10de9d) #1 h264_initialise_ref_list ffmpeg/libavcodec/h264_refs.c:214:29 (ffmpeg+0x1186b3f) #2 ff_h264_build_ref_list ffmpeg/libavcodec/h264_refs.c:306 (ffmpeg+0x1186b3f) #3 h264_slice_init ffmpeg/libavcodec/h264_slice.c:1900:11 (ffmpeg+0x1191149) [..] Previous read of size 8 at 0x7bbc000082a8 by main thread (mutexes: write M1630): #0 memcpy /work/release-test/final/llvm.src/projects/compiler-rt/lib/tsan/../sanitizer_common/sanitizer_common_interceptors.inc:655:5 (ffmpeg+0x10de9d) #1 ff_h264_update_thread_context ffmpeg/libavcodec/h264_slice.c:411:5 (ffmpeg+0x118b7dc) Signed-off-by: Wan-Teh Chang <wtc@google.com> --- libavcodec/h264_slice.c | 1 - 1 file changed, 1 deletion(-)