diff --git a/runtime/hsa-runtime/core/runtime/amd_gpu_agent.cpp b/runtime/hsa-runtime/core/runtime/amd_gpu_agent.cpp
index a606159892..59d21bb2e6 100644
--- a/runtime/hsa-runtime/core/runtime/amd_gpu_agent.cpp
+++ b/runtime/hsa-runtime/core/runtime/amd_gpu_agent.cpp
@@ -504,6 +504,7 @@ void GpuAgent::InitScratchPool() {
 void GpuAgent::ReserveScratch()
 {
   size_t reserved_sz = core::Runtime::runtime_singleton_->flag().scratch_single_limit();
+  ScopedAcquire<KernelMutex> lock(&scratch_lock_);
   if (!scratch_cache_.reserved_bytes() && reserved_sz) {
     HSAuint64 alt_va;
     void* reserved_base = scratch_pool_.alloc(reserved_sz);