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d3d12: Fix fence signal race when no command lists are submitted 

Signaling a fence in Dawn without waiting can cause a race between Dawn
and Chromium over who signals the fence. Since D3D12 fences are allowed
to be rewound this can cause future waits to hang indefinitely if Dawn
loses the race and signals a lower value than what Chromium expects.

The signal without wait case happens when Dawn submits no command lists
e.g. when CopyExternalImageToTexture uses a zero-sized dimension. This
is the reason for the test failures in https://crrev.com/c/3700811 e.g.
https://ci.chromium.org/ui/p/chromium/builders/try/dawn-win10-x64-deps-rel/24617/overview

To fix the race, it's sufficient to wait before signaling if not already
waited which is what this CL does. This CL also makes the fence stay
alive until pending signals are done - this wasn't the root cause of the
hang described above, but it's still a good idea for robustness, and
also recommended based on discussion around past Chromium XR fence use.

Bug: dawn:576
Change-Id: I8c1d1a19fdb022ae28d26f6723c2f2bfc9c1c3c7
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/96321
Auto-Submit: Sunny Sachanandani <sunnyps@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Sunny Sachanandani <sunnyps@chromium.org>
This commit is contained in:
Sunny Sachanandani 2022-07-18 22:04:52 +00:00 committed by Dawn LUCI CQ
parent 4a92a3c904
commit 6cbe015429
2 changed files with 14 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
src/dawn/native/d3d12/ExternalImageDXGIImpl.cpp
View File

@ -62,7 +62,12 @@ bool ExternalImageDXGIImpl::IsValid() const {
void ExternalImageDXGIImpl::Destroy() {
if (IsInList()) {
RemoveFromList();
// Keep fence alive until any pending signal calls are done on the GPU.
mBackendDevice->ConsumedError(mBackendDevice->NextSerial());
mBackendDevice->ReferenceUntilUnused(mD3D12Fence.Get());
mBackendDevice = nullptr;
mD3D12Resource.Reset();
mD3D12Fence.Reset();
mD3D11on12ResourceCache.reset();

10
src/dawn/native/d3d12/TextureD3D12.cpp
View File

@ -675,7 +675,15 @@ void Texture::DestroyImpl() {
// Signal the fence on destroy after all uses of the texture.
if (mD3D12Fence != nullptr && mFenceSignalValue != 0) {
device->GetCommandQueue()->Signal(mD3D12Fence.Get(), mFenceSignalValue);
// Enqueue a fence wait if we haven't already; otherwise the fence signal will be racy.
if (mFenceWaitValue != UINT64_MAX) {
device->ConsumedError(
CheckHRESULT(device->GetCommandQueue()->Wait(mD3D12Fence.Get(), mFenceWaitValue),
"D3D12 fence wait"));
}
device->ConsumedError(
CheckHRESULT(device->GetCommandQueue()->Signal(mD3D12Fence.Get(), mFenceSignalValue),
"D3D12 fence signal"));
}
// Now that the texture has been destroyed. It should release the refptr of the d3d11on12