vulkan: when using transfer queue for async copies, sync on event_wait to avoid race

ggml/src/ggml-vulkan/ggml-vulkan.cpp

@@ -7687,6 +7687,20 @@ static vk_context ggml_vk_get_compute_ctx(ggml_backend_vk_context * ctx) {
     return result;
 }
 
+static vk_context ggml_vk_get_transfer_ctx(ggml_backend_vk_context * ctx) {
+    vk_context result;
+    if (!ctx->transfer_ctx.expired()) {
+        result = ctx->transfer_ctx.lock();
+    } else {
+        result = ggml_vk_create_context(ctx, ctx->transfer_cmd_pool);
+
+        ctx->transfer_ctx = result;
+        ggml_vk_ctx_begin(ctx->device, result);
+    }
+
+    return result;
+}
+
 // Submit any pending transfer queue work and signal the transfer semaphore.
 // The next compute context created via ggml_vk_get_compute_ctx will wait on this semaphore.
 // Returns true if work was submitted.
@@ -15456,13 +15470,7 @@ static void ggml_backend_vk_set_tensor_2d_async(ggml_backend_t backend, ggml_ten
     vk_context cpy_ctx;
 
     if (ctx->device->async_use_transfer_queue) {
-        if (ctx->transfer_ctx.expired()) {
-            cpy_ctx = ggml_vk_create_context(ctx, ctx->transfer_cmd_pool);
-            ctx->transfer_ctx = cpy_ctx;
-            ggml_vk_ctx_begin(ctx->device, cpy_ctx);
-        } else {
-            cpy_ctx = ctx->transfer_ctx.lock();
-        }
+        cpy_ctx = ggml_vk_get_transfer_ctx(ctx);
     } else {
         cpy_ctx = ggml_vk_get_compute_ctx(ctx);
     }
@@ -15608,13 +15616,7 @@ static bool ggml_backend_vk_cpy_tensor_async(ggml_backend_t backend_src, ggml_ba
 
         vk_context cpy_ctx;
         if (ctx->device->async_use_transfer_queue) {
-            if (ctx->transfer_ctx.expired()) {
-                cpy_ctx = ggml_vk_create_context(ctx, ctx->transfer_cmd_pool);
-                ctx->transfer_ctx = cpy_ctx;
-                ggml_vk_ctx_begin(ctx->device, cpy_ctx);
-            } else {
-                cpy_ctx = ctx->transfer_ctx.lock();
-            }
+            cpy_ctx = ggml_vk_get_transfer_ctx(ctx);
         } else {
             cpy_ctx = ggml_vk_get_compute_ctx(ctx);
         }
@@ -16935,6 +16937,11 @@ static void ggml_backend_vk_event_wait(ggml_backend_t backend, ggml_backend_even
     if (vkev->has_event) {
         // Wait for latest event
         ggml_vk_wait_events(compute_ctx, { vkev->event });
+
+        if (ctx->device->async_use_transfer_queue) {
+            vk_context transfer_ctx = ggml_vk_get_transfer_ctx(ctx);
+            transfer_ctx->s->wait_semaphores.push_back(vkev->tl_semaphore);
+        }
     }
 }