cellVdec: Postpone Context Destruction

rpcs3/Emu/Cell/Modules/cellVdec.cpp

@@ -298,9 +298,15 @@ struct vdec_context final
 	}
 
 	~vdec_context()
+	{
+		release_decoder();
+	}
+
+	// Frees the FFmpeg decoder, which may take milliseconds
+	void release_decoder()
 	{
 		avcodec_free_context(&ctx);
-		sws_freeContext(sws);
+		sws_freeContext(std::exchange(sws, nullptr));
 	}
 
 	static u32 freq_to_framerate_code(f64 freq)
@@ -653,6 +659,38 @@ struct vdec_context final
 	}
 };
 
+// Frees the FFmpeg decoders of closed contexts on a host thread.
+// Freeing a decoder takes milliseconds, which would otherwise delay the guest thread closing it.
+struct vdec_context_reaper
+{
+	lf_queue<shared_ptr<vdec_context>> contexts;
+
+	void operator()()
+	{
+		while (thread_ctrl::state() != thread_state::aborting)
+		{
+			thread_ctrl::wait_on(contexts);
+
+			// Let the closing sequence of the caller complete first: freeing this much memory slows down the other threads
+			thread_ctrl::wait_for(100'000);
+
+			for (auto&& vdec : contexts.pop_all())
+			{
+				if (vdec.use_count() > 1)
+				{
+					// Still used by an HLE call in progress, retry later
+					contexts.push(std::move(vdec));
+					continue;
+				}
+
+				vdec->release_decoder();
+			}
+		}
+	}
+
+	static constexpr auto thread_name = "HLE Video Decoder Reaper"sv;
+};
+
 extern bool check_if_vdec_contexts_exist()
 {
 	bool context_exists = false;
@@ -1493,12 +1531,15 @@ error_code cellVdecClose(ppu_thread& ppu, u32 handle)
 	vdec->seq_state = sequence_state::closed;
 	vdec->mutex.lock_unlock();
 
-	if (!idm::remove_verify<vdec_context>(handle, std::move(vdec)))
+	if (!idm::remove_verify<vdec_context>(handle, vdec))
 	{
 		// Other thread removed it beforehead
 		return { CELL_VDEC_ERROR_ARG, "remove_verify failed" };
 	}
 
+	// Let the reaper free the decoder so that the caller does not pay for it
+	g_fxo->get<named_thread<vdec_context_reaper>>().contexts.push(std::move(vdec));
+
 	return CELL_OK;
 }