Sync needed when wrapping around the kernel arg buffer

If we issue too many copy commands without syncing and wrapping happens,
we need to wait for the blits to be done before moving forward otherwise
we will overwrite the kernel args of the blits in flight.

Change-Id: I9a21e31ce07f8e8157ca38e96dc264ff47fd3639

runtime/hsa-runtime/core/runtime/amd_blit_kernel.cpp

@@ -785,12 +785,8 @@ uint64_t BlitKernel::AcquireWriteIndex(uint32_t num_packet) {
 
   uint64_t write_index = queue_->AddWriteIndexAcqRel(num_packet);
 
-  while (true) {
-    // Wait until we have room in the queue;
-    const uint64_t read_index = queue_->LoadReadIndexRelaxed();
-    if ((write_index - read_index) <= queue_->public_handle()->size) {
-      break;
-    }
+  while (write_index + num_packet - queue_->LoadReadIndexRelaxed() > queue_->public_handle()->size) {
+    os::YieldThread();
   }
 
   return write_index;
@@ -887,8 +883,9 @@ void BlitKernel::PopulateQueue(uint64_t index, uint64_t code_handle, void* args,
 
 BlitKernel::KernelArgs* BlitKernel::ObtainAsyncKernelCopyArg() {
   const uint32_t index =
-      atomic::Add(&kernarg_async_counter_, 1U, std::memory_order_acquire);
-  KernelArgs* arg = &kernarg_async_[index & kernarg_async_mask_];
+      atomic::Add(&kernarg_async_counter_, 1U, std::memory_order_acquire) & kernarg_async_mask_;
+
+  KernelArgs* arg = &kernarg_async_[index];
   assert(IsMultipleOf(arg, 16));
   return arg;
 }