Apr 17, 2023, 11:25 by an...@khirnov.net: > Quoting Lynne (2023-03-14 07:33:43) > >> From 6e2dfc44e50798264eb16bc2dcabfdbf2fbac2d7 Mon Sep 17 00:00:00 2001 >> From: Lynne <d...@lynne.ee> >> Date: Thu, 15 Dec 2022 01:06:52 +0100 >> Subject: [PATCH 24/92] hwconfig: add a new HWACCEL_CAP_THREAD_SAFE for >> threadsafe hwaccels >> >> Vulkan is fully threadsafe and stateless, so we can benefit from this. >> --- >> libavcodec/hwconfig.h | 1 + >> libavcodec/pthread_frame.c | 2 +- >> 2 files changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/libavcodec/hwconfig.h b/libavcodec/hwconfig.h >> index 721424912c..e6b78f0160 100644 >> --- a/libavcodec/hwconfig.h >> +++ b/libavcodec/hwconfig.h >> @@ -24,6 +24,7 @@ >> >> >> #define HWACCEL_CAP_ASYNC_SAFE (1 << 0) >> +#define HWACCEL_CAP_THREAD_SAFE (1 << 1) >> >> >> typedef struct AVCodecHWConfigInternal { >> diff --git a/libavcodec/pthread_frame.c b/libavcodec/pthread_frame.c >> index 74864e19c5..c096287233 100644 >> --- a/libavcodec/pthread_frame.c >> +++ b/libavcodec/pthread_frame.c >> @@ -204,7 +204,7 @@ static attribute_align_arg void >> *frame_worker_thread(void *arg) >> >> /* if the previous thread uses hwaccel then we take the lock to ensure >> * the threads don't run concurrently */ >> - if (avctx->hwaccel) { >> + if (avctx->hwaccel && !(avctx->hwaccel->caps_internal & >> HWACCEL_CAP_THREAD_SAFE)) { >> > > A major problem here is that hwaccel_priv_data exists in only a single > instance shared across all the worker threads. If you want frame-threaded > hwaccels, you'll need to add some mechanism for synchronizing it between > threads. > > I really wonder how does your code survive all the races involved. >
It works because hwaccel_priv_data is read-only. No need to synchronize anything, the contexts Vulkan creates are defined as driver-synchronized, and all the info a frame needs is provided when decoding it, rather than kept as a state. So I don't see a problem here. _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".