diff --git a/ggml/src/ggml-webgpu/ggml-webgpu.cpp b/ggml/src/ggml-webgpu/ggml-webgpu.cpp
index 7f2f9ecc4d..d1723ff73f 100644
--- a/ggml/src/ggml-webgpu/ggml-webgpu.cpp
+++ b/ggml/src/ggml-webgpu/ggml-webgpu.cpp
@@ -146,8 +146,13 @@ struct webgpu_submission_futures {
 struct webgpu_buf_pool {
     std::vector<webgpu_pool_bufs> free;
 
+    // The pool must be synchronized because:
+    // 1. The memset pool is shared globally by every ggml buffer,
+    // since allocating a pool per ggml buffer would consume too much memory.
+    // 2. For the per-thread buffer pools in webgpu_context,
+    // buffers are allocated and freed in Dawn callbacks,
+    // which can run on a different thread than the calling thread.
     std::mutex mutex;
-
     std::condition_variable cv;
 
     void init(wgpu::Device      device,