GPU: Add SyncToken::ToDebugString()

This is intended as a convenience for debugging synchronization issues
related to sync tokens.

The output is in the format "a:b:c:d", i.e. "0:1:4:16", where a is
the namespace_id, b/c are the upper and lower half of the 64bit command
buffer ID (corresponding to channel and route ID for gpu/ipc/ usage),
and d is the release count.

Change-Id: I2cbc1ce9cff56d8b83bfa582ce4702f7459005c3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2324869
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Auto-Submit: Klaus Weidner <klausw@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Sunny Sachanandani <sunnyps@chromium.org>
Reviewed-by: Piotr Bialecki <bialpio@chromium.org>
Cr-Commit-Position: refs/heads/master@{#794776}

chrome/browser/android/vr/arcore_device/ar_image_transport.cc

@@ -172,7 +172,8 @@ bool ArImageTransport::ResizeSharedBuffer(vr::WebXrPresentationState* webxr,
   buffer->mailbox_holder = mailbox_bridge_->CreateSharedImage(
       buffer->gmb.get(), gfx::ColorSpace(), shared_image_usage);
   DVLOG(2) << ": CreateSharedImage, mailbox="
-           << buffer->mailbox_holder.mailbox.ToDebugString();
+           << buffer->mailbox_holder.mailbox.ToDebugString() << ", SyncToken="
+           << buffer->mailbox_holder.sync_token.ToDebugString();
 
   auto img = base::MakeRefCounted<gl::GLImageAHardwareBuffer>(size);
 
@@ -230,6 +231,8 @@ gpu::MailboxHolder ArImageTransport::TransferFrame(
   // that it's transitioned through "processing" and "rendering" states back
   // to "animating".
   DCHECK(shared_buffer->mailbox_holder.sync_token.HasData());
+  DVLOG(2) << ": SyncToken="
+           << shared_buffer->mailbox_holder.sync_token.ToDebugString();
 
   return shared_buffer->mailbox_holder;
 }

gpu/command_buffer/common/sync_token.cc

@@ -4,6 +4,8 @@
 
 #include "gpu/command_buffer/common/sync_token.h"
 
+#include <sstream>
+
 namespace gpu {
 
 SyncToken::SyncToken()
@@ -21,4 +23,19 @@ SyncToken::SyncToken(CommandBufferNamespace namespace_id,
 
 SyncToken::SyncToken(const SyncToken& other) = default;
 
+std::string SyncToken::ToDebugString() const {
+  // At the level of the generic command buffer code, the command buffer ID is
+  // an arbitrary 64-bit number. For the debug output, print its upper and lower
+  // 32bit words separately. This ensures more readable output for IDs allocated
+  // by gpu/ipc code which uses these words for channel and route IDs, but it's
+  // still a lossless representation if the IDs don't match this convention.
+  uint64_t id = command_buffer_id().GetUnsafeValue();
+  uint32_t channel_or_high = 0xffffffff & id;
+  uint32_t route_or_low = id >> 32;
+  std::ostringstream stream;
+  stream << static_cast<int>(namespace_id()) << ":" << channel_or_high << ":"
+         << route_or_low << ":" << release_count();
+  return stream.str();
+}
+
 }  // namespace gpu

gpu/command_buffer/common/sync_token.h

@@ -83,6 +83,8 @@ struct GPU_EXPORT SyncToken {
 
   bool operator!=(const SyncToken& other) const { return !(*this == other); }
 
+  std::string ToDebugString() const;
+
  private:
   bool verified_flush_;
   CommandBufferNamespace namespace_id_;

third_party/blink/renderer/platform/graphics/gpu/xr_webgl_drawing_buffer.cc

@@ -216,8 +216,6 @@ IntSize XRWebGLDrawingBuffer::AdjustSize(const IntSize& new_size) {
 
 void XRWebGLDrawingBuffer::UseSharedBuffer(
     const gpu::MailboxHolder& buffer_mailbox_holder) {
-  DVLOG(3) << __FUNCTION__;
-
   gpu::gles2::GLES2Interface* gl = drawing_buffer_->ContextGL();
 
   // Ensure that the mailbox holder is ready to use, the following actions need
@@ -228,6 +226,10 @@ void XRWebGLDrawingBuffer::UseSharedBuffer(
   // recovery for cases where these assumptions may not be accurate.
   DCHECK(buffer_mailbox_holder.sync_token.HasData());
   DCHECK(!buffer_mailbox_holder.mailbox.IsZero());
+  DVLOG(3) << __func__
+           << ": mailbox=" << buffer_mailbox_holder.mailbox.ToDebugString()
+           << ", SyncToken="
+           << buffer_mailbox_holder.sync_token.ToDebugString();
   gl->WaitSyncTokenCHROMIUM(buffer_mailbox_holder.sync_token.GetConstData());
 
   // Create a texture backed by the shared buffer image.