Use GetMappedRange early but still get null pointer sometimes

filament/backend/src/webgpu/WebGPUBufferBase.cpp

@@ -94,15 +94,14 @@ void WebGPUBufferBase::updateGPUBuffer(BufferDescriptor const& bufferDescriptor,
     //     .size = stagingBufferSize,
     //     .mappedAtCreation = true };
     // wgpu::Buffer stagingBuffer = device.CreateBuffer(&descriptor);
-    wgpu::Buffer stagingBuffer = webGPUStagePool->acquireBuffer(stagingBufferSize);
+    MappedStage mappedStage = webGPUStagePool->acquireBuffer(stagingBufferSize);
 
-    void* mappedRange = stagingBuffer.GetMappedRange();
-    std::string mappedRangeIsNull = mappedRange
+    std::string mappedRangeIsNull = mappedStage.mappedRange
             ? "no"
             : "yes";
     std::cout << "Run Yu: got mapped range on the staging buffer with size "
-              << stagingBuffer.GetSize() << " and it is null? " <<  mappedRangeIsNull << std::endl;
-    memcpy(mappedRange, bufferDescriptor.buffer, bufferDescriptor.size);
+              << mappedStage.buffer.GetSize() << " and it is null? " <<  mappedRangeIsNull << std::endl;
+    memcpy(mappedStage.mappedRange, bufferDescriptor.buffer, bufferDescriptor.size);
 
     // Make sure the padded memory is set to 0 to have deterministic behaviors
     // if (remainder != 0) {
@@ -117,13 +116,13 @@ void WebGPUBufferBase::updateGPUBuffer(BufferDescriptor const& bufferDescriptor,
     //     memset(paddingStart, 0, FILAMENT_WEBGPU_BUFFER_SIZE_MODULUS - (stagingBuffer.GetSize() - bufferDescriptor.size));
     // }
 
-    stagingBuffer.Unmap();
+    mappedStage.buffer.Unmap();
 
     std::cout << "Run Yu: about to issue copy command with actual staging buffer of size "
-              << stagingBuffer.GetSize() << ", and computed size of " << stagingBufferSize
+              << mappedStage.buffer.GetSize() << ", and computed size of " << stagingBufferSize
               << ". The mBuffer size is " << mBuffer.GetSize() << std::endl;
     // Copy the staging buffer contents to the destination buffer.
-    webGPUQueueManager->getCommandEncoder().CopyBufferToBuffer(stagingBuffer, 0, mBuffer,
+    webGPUQueueManager->getCommandEncoder().CopyBufferToBuffer(mappedStage.buffer, 0, mBuffer,
             byteOffset,
             remainder == 0 ? bufferDescriptor.size
                            : mainBulk + FILAMENT_WEBGPU_BUFFER_SIZE_MODULUS);
@@ -134,8 +133,8 @@ void WebGPUBufferBase::updateGPUBuffer(BufferDescriptor const& bufferDescriptor,
         WebGPUStagePool* webGPUStagePool;
     };
     auto userData = std::make_unique<UserData>(
-            UserData{ .stagingBuffer = stagingBuffer, .webGPUStagePool = webGPUStagePool });
-    stagingBuffer.MapAsync(
+            UserData{ .stagingBuffer = mappedStage.buffer, .webGPUStagePool = webGPUStagePool });
+    mappedStage.buffer.MapAsync(
             wgpu::MapMode::Write, 0, stagingBufferSize, wgpu::CallbackMode::AllowSpontaneous,
             [](wgpu::MapAsyncStatus status, const char* message, UserData* userData) {
                 if (UTILS_LIKELY(status == wgpu::MapAsyncStatus::Success)) {

filament/backend/src/webgpu/WebGPUStagePool.cpp

@@ -26,24 +26,32 @@ WebGPUStagePool::WebGPUStagePool(wgpu::Device const& device) : mDevice(device) {
 
 WebGPUStagePool::~WebGPUStagePool() = default;
 
-wgpu::Buffer WebGPUStagePool::acquireBuffer(size_t requiredSize) {
+MappedStage WebGPUStagePool::acquireBuffer(size_t requiredSize) {
     std::cout << "Run Yu: required size in acquireBuffer: " << requiredSize << std::endl;
     std::cout << "Run Yu: the pool size is " << mBuffers.size() << std::endl;
     {
         std::lock_guard<std::mutex> lock(mMutex);
         auto iter = mBuffers.lower_bound(requiredSize);
         if (iter != mBuffers.end()) {
-            wgpu::Buffer bufferFromPool = iter->second;
-            std::cout << "Run Yu: found buffer in the pool with size " << bufferFromPool.GetSize()
+            std::cout << "Run Yu: found buffer in the pool with size " << iter->second.GetSize()
                       << std::endl;
-            mBuffers.erase(iter);
-            if (bufferFromPool.GetMapState() != wgpu::BufferMapState::Mapped) {
-                std::cout << "Run Yu: buffer from pool is not mapped!!" << std::endl;
+            if (iter->second.GetMapState() != wgpu::BufferMapState::Mapped) {
+                std::cout << "Run Yu: before GetMappedRange the buffer state is not mapped!\n";
             }
-            return bufferFromPool;
+            MappedStage mappedStage = { .buffer = iter->second,
+                .mappedRange = iter->second.GetMappedRange() };
+            if (!mappedStage.mappedRange) {
+                std::cout << "Run Yu: mapped range is null in acquireBuffer!\n";
+            }
+            if (mappedStage.buffer.GetMapState() != wgpu::BufferMapState::Mapped) {
+                std::cout << "Run Yu: after GetMappedRange the buffer state is not mapped!\n";
+            }
+            mBuffers.erase(iter);
+            return mappedStage;
         }
     }
-    return createNewBuffer(requiredSize);
+    wgpu::Buffer newBuffer = createNewBuffer(requiredSize);
+    return { .buffer = newBuffer, .mappedRange = newBuffer.GetMappedRange() };
 }
 
 void WebGPUStagePool::addBufferToPool(wgpu::Buffer buffer) {
@@ -64,8 +72,6 @@ void WebGPUStagePool::addBufferToPool(wgpu::Buffer buffer) {
     }
     if (!allMapped) {
         std::cout << "Run Yu: found buffers that are not mapped\n";
-    } else {
-        std::cout << "Run Yu: all buffers are mapped\n";
     }
 }
 

filament/backend/src/webgpu/WebGPUStagePool.h

@@ -24,12 +24,17 @@
 
 namespace filament::backend {
 
+struct MappedStage {
+    wgpu::Buffer buffer;
+    void* mappedRange;
+};
+
 class WebGPUStagePool {
 public:
     WebGPUStagePool(wgpu::Device const& device);
     ~WebGPUStagePool();
 
-    wgpu::Buffer acquireBuffer(size_t requiredSize);
+    MappedStage acquireBuffer(size_t requiredSize);
     void addBufferToPool(wgpu::Buffer buffer);
 private:
     wgpu::Buffer createNewBuffer(size_t bufferSize);