Hi Ronald, A variant of this patch is committed as 2e664b9c1e73c80aab91070c1eb7676f04bdd12d:
http://ffmpeg.org/pipermail/ffmpeg-cvslog/2017-April/106577.html I believe it does not fix the tsan warning. On Thu, Apr 6, 2017 at 10:48 AM, Ronald S. Bultje <rsbul...@gmail.com> wrote: > ..., but this way the accesses to the > field (reads and writes) are always protected by a mutex. The patch protects the reads of the |debug| field with p->progress_mutex, where |p| points to a PerThreadContext. But the write of the |debug| field in update_context_from_user() is not protected by progress_mutex of any PerThreadContext. The tsan warning this patch tried to fix is: > WARNING: ThreadSanitizer: data race (pid=10916) > Write of size 4 at 0x7d64000174fc by main thread (mutexes: write M2313): > #0 update_context_from_user src/libavcodec/pthread_frame.c:335 > (ffmpeg+0x000000df7b06) > [..] > Previous read of size 4 at 0x7d64000174fc by thread T1 (mutexes: write > M2311): > #0 ff_thread_await_progress src/libavcodec/pthread_frame.c:592 > (ffmpeg+0x000000df8b3e) The code in libavcodec/pthread_frame.c related to the write of the |debug| field shown in the tsan warning is the following: 326 static int update_context_from_user(AVCodecContext *dst, AVCodecContext *sr c) 327 { ,,, 333 334 dst->opaque = src->opaque; 335 dst->debug = src->debug; 336 dst->debug_mv = src->debug_mv; ... 383 static int submit_packet(PerThreadContext *p, AVCodecContext *user_avctx, 384 AVPacket *avpkt) 385 { ... 393 394 pthread_mutex_lock(&p->mutex); 395 396 ret = update_context_from_user(p->avctx, user_avctx); ... 472 int ff_thread_decode_frame(AVCodecContext *avctx, 473 AVFrame *picture, int *got_picture_ptr, 474 AVPacket *avpkt) 475 { ... 480 481 /* release the async lock, permitting blocked hwaccel threads to 482 * go forward while we are in this function */ 483 async_unlock(fctx); 484 485 /* 486 * Submit a packet to the next decoding thread. 487 */ 488 489 p = &fctx->threads[fctx->next_decoding]; 490 err = submit_packet(p, avctx, avpkt); The code snippets show the write of dst->debug is only protected by p->mutex (acquired at line 394) for some |p|. progress_mutex (of any AVCodecContext) is not involved at all. Wan-Teh Chang _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
