[FFmpeg-devel,v3,1/2] dnn_backend_native_layer_conv2d.c: fix memory allocation bug in multithread function.

diff --git a/libavfilter/dnn/dnn_backend_native_layer_conv2d.c b/libavfilter/dnn/dnn_backend_native_layer_conv2d.c
index c52725aa2b..5c313454f7 100644
--- a/libavfilter/dnn/dnn_backend_native_layer_conv2d.c
+++ b/libavfilter/dnn/dnn_backend_native_layer_conv2d.c
@@ -32,6 +32,7 @@  typedef struct thread_common_param{
     int32_t output_operand_index;
     const void *parameters;
     NativeContext *ctx;
+    float *output_data;
     int thread_num;
 } thread_common_param;
 
@@ -111,9 +112,7 @@  static void * dnn_execute_layer_conv2d_thread(void *threadarg)
     thread_param *thread_param = (struct thread_param *)threadarg;
     thread_common_param *thread_common_param = thread_param->thread_common_param;
     DnnOperand *operands = thread_common_param->operands;
-    float *output;
     int32_t input_operand_index = thread_common_param->input_operand_indexes[0];
-    int number = operands[input_operand_index].dims[0];
     int height = operands[input_operand_index].dims[1];
     int width = operands[input_operand_index].dims[2];
     int channel = operands[input_operand_index].dims[3];
@@ -130,24 +129,7 @@  static void * dnn_execute_layer_conv2d_thread(void *threadarg)
     int thread_start = thread_stride * thread_param->thread_index + pad_size;
     int thread_end = (thread_param->thread_index == thread_common_param->thread_num - 1) ? (height - pad_size) : (thread_start + thread_stride);
 
-    DnnOperand *output_operand = &operands[thread_common_param->output_operand_index];
-    output_operand->dims[0] = number;
-    output_operand->dims[1] = height - pad_size * 2;
-    output_operand->dims[2] = width - pad_size * 2;
-    output_operand->dims[3] = conv_params->output_num;
-    output_operand->data_type = operands[input_operand_index].data_type;
-    output_operand->length = calculate_operand_data_length(output_operand);
-    if (output_operand->length <= 0) {
-        av_log(thread_common_param->ctx, AV_LOG_ERROR, "The output data length overflow\n");
-        return (void *)DNN_ERROR;
-    }
-    output_operand->data = av_realloc(output_operand->data, output_operand->length);
-    if (!output_operand->data) {
-        av_log(thread_common_param->ctx, AV_LOG_ERROR, "Failed to reallocate memory for output\n");
-        return (void *)DNN_ERROR;
-    }
-
-    output = output_operand->data;
+    float *output = thread_common_param->output_data;
     output += (conv_params->output_num) * (width - 2 * pad_size) * (thread_start - pad_size);
 
     av_assert0(channel == conv_params->input_num);
@@ -213,16 +195,33 @@  int dnn_execute_layer_conv2d(DnnOperand *operands, const int32_t *input_operand_
     pthread_t *thread_id = av_malloc(thread_num * sizeof(pthread_t));
 #endif
     thread_param **thread_param = av_malloc(thread_num * sizeof(*thread_param));
-    void *res;
-    int error_flag = DNN_SUCCESS;
-
-    //struct used to pass parameters
     thread_common_param thread_common_param;
+    const ConvolutionalParams *conv_params = (const ConvolutionalParams *)(parameters);
+    int pad_size = (conv_params->padding_method == VALID) ? (conv_params->kernel_size - 1) / 2 * conv_params->dilation : 0;
+    DnnOperand *output_operand = &operands[output_operand_index];
+
+    output_operand->dims[0] = operands[input_operand_indexes[0]].dims[0];
+    output_operand->dims[1] = operands[input_operand_indexes[0]].dims[1] - pad_size * 2;
+    output_operand->dims[2] = operands[input_operand_indexes[0]].dims[2] - pad_size * 2;
+    output_operand->dims[3] = conv_params->output_num;
+    output_operand->data_type = operands[input_operand_indexes[0]].data_type;
+    output_operand->length = calculate_operand_data_length(output_operand);
+    if (output_operand->length <= 0) {
+        av_log(ctx, AV_LOG_ERROR, "The output data length overflow\n");
+        return DNN_ERROR;
+    }
+    output_operand->data = av_realloc(output_operand->data, output_operand->length);
+    if (!output_operand->data) {
+        av_log(ctx, AV_LOG_ERROR, "Failed to reallocate memory for output\n");
+        return DNN_ERROR;
+    }
+    thread_common_param.output_data = output_operand->data;
     thread_common_param.operands = operands;
     thread_common_param.input_operand_indexes = input_operand_indexes;
     thread_common_param.output_operand_index = output_operand_index;
     thread_common_param.parameters = parameters;
     thread_common_param.ctx = ctx;
+
 #if HAVE_PTHREAD_CANCEL
     thread_common_param.thread_num = thread_num;
 
@@ -236,9 +235,7 @@  int dnn_execute_layer_conv2d(DnnOperand *operands, const int32_t *input_operand_
 
     //join threads, res gets function return
     for (int i = 0; i < thread_num; i++){
-        pthread_join(thread_id[i], &res);
-        if ((int)res != DNN_SUCCESS)
-            error_flag = (int)res;
+        pthread_join(thread_id[i], NULL);
     }
 
     //release memory
@@ -252,12 +249,10 @@  int dnn_execute_layer_conv2d(DnnOperand *operands, const int32_t *input_operand_
     thread_param[0] = av_malloc(sizeof(thread_param));
     thread_param[0]->thread_common_param = &thread_common_param;
     thread_param[0]->thread_index = 0;
-    res = dnn_execute_layer_conv2d_thread((void *)thread_param[0]);
-    if ((int)res != DNN_SUCCESS)
-        error_flag = (int)res;
+    dnn_execute_layer_conv2d_thread((void *)thread_param[0]);
     av_free(thread_param[0]);
 #endif
 
     av_free(thread_param);
-    return error_flag;
+    return DNN_SUCCESS;
 }