[PR] avfilter/dnn: fix teardown hang in ONNX backend (PR #24259)

PR #24259 opened by Steven Xiao (younengxiao)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24259
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24259.patch

This is used to fix the bug introduced by https://github.com/FFmpeg/FFmpeg/commit/b52c71e43813952650a74c57b2f31bd0166600ba .

dnn_free_model_onnx() waits for the request queue to reach ctx->nireq
items, but dnn_load_model_onnx() only ever allocates one. With
nireq >= 2 that wait can never succeed and teardown hangs forever.

ONNX inference is synchronous, so every request has already finished
by the time teardown runs. Drop the wait.



>From 1e38c83eaf937e17eb6f10063cbaccb111033c70 Mon Sep 17 00:00:00 2001
From: younengxiao <[email protected]>
Date: Mon, 24 Aug 2026 20:44:32 -0400
Subject: [PATCH] avfilter/dnn: fix teardown hang in ONNX backend

dnn_free_model_onnx() waits for the request queue to reach ctx->nireq
items, but dnn_load_model_onnx() only ever allocates one. With
nireq >= 2 that wait can never succeed and teardown hangs forever.

ONNX inference is synchronous, so every request has already finished
by the time teardown runs. Drop the wait.

Signed-off-by: younengxiao <[email protected]>
---
 libavfilter/dnn/dnn_backend_onnx.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/libavfilter/dnn/dnn_backend_onnx.c b/libavfilter/dnn/dnn_backend_onnx.c
index 6c75d6eb24..4c36cb7cbc 100644
--- a/libavfilter/dnn/dnn_backend_onnx.c
+++ b/libavfilter/dnn/dnn_backend_onnx.c
@@ -152,7 +152,11 @@ static void dnn_free_model_onnx(DNNModel **model)
 
     onnx_model = (ONNXModel *)(*model);
 
-    ff_dnn_wait_requests(onnx_model->request_queue, onnx_model->ctx->nireq);
+    /*
+     * Inference runs synchronously here: execute_model_onnx() completes the
+     * inference and its callback before returning, and async execution is
+     * rejected with ENOSYS.
+     */
     while (ff_safe_queue_size(onnx_model->request_queue) != 0) {
         ONNXRequestItem *item = (ONNXRequestItem *)ff_safe_queue_pop_front(onnx_model->request_queue);
         destroy_request_item(&item);
-- 
2.52.0

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