2 files changed, 41 insertions, 3 deletions
diff --git a/gpu/command_buffer/common/cmd_buffer_common.h b/gpu/command_buffer/common/cmd_buffer_common.h
index e8bcd43..80d1e28 100644
--- a/gpu/command_buffer/common/cmd_buffer_common.h
+++ b/gpu/command_buffer/common/cmd_buffer_common.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
@@ -157,6 +157,7 @@ namespace cmd {
   OP(SetBucketDataImmediate)        /*  9 */ \
   OP(GetBucketSize)                 /* 10 */ \
   OP(GetBucketData)                 /* 11 */ \
+  OP(YieldScheduler)                /* 12 */ \
 
 // Common commands.
 enum CommandId {
@@ -641,6 +642,32 @@ COMPILE_ASSERT(offsetof(GetBucketData, shared_memory_id) == 16,
 COMPILE_ASSERT(offsetof(GetBucketData, shared_memory_offset) == 20,
                Offsetof_GetBucketData_shared_memory_offset_not_20);
 
+// A Yield command. Hints the scheduler that this is a good point to update the
+// state and schedule other command buffers.
+struct YieldScheduler {
+  typedef YieldScheduler ValueType;
+  static const CommandId kCmdId = kYieldScheduler;
+  static const cmd::ArgFlags kArgFlags = cmd::kFixed;
+
+  void SetHeader() {
+    header.SetCmd<ValueType>();
+  }
+
+  void Init() {
+    SetHeader();
+  }
+  static void* Set(void* cmd) {
+    static_cast<ValueType*>(cmd)->Init();
+    return NextCmdAddress<ValueType>(cmd);
+  }
+
+  CommandHeader header;
+};
+
+COMPILE_ASSERT(sizeof(YieldScheduler) == 4, Sizeof_YieldScheduler_is_not_4);
+COMPILE_ASSERT(offsetof(YieldScheduler, header) == 0,
+               Offsetof_YieldScheduler_header_not_0);
+
 }  // namespace cmd
 
 #pragma pack(pop)
diff --git a/gpu/command_buffer/common/constants.h b/gpu/command_buffer/common/constants.h
index ca1d5a8..3b06cad 100644
--- a/gpu/command_buffer/common/constants.h
+++ b/gpu/command_buffer/common/constants.h
@@ -26,12 +26,23 @@ namespace error {
     // This is not an error. It is returned by WaitLatch when it is blocked.
     // When blocked, the context will not reschedule itself until another
     // context executes a SetLatch command.
-    kWaiting
+    kWaiting,
+
+    // This is not an error either. It just hints the scheduler that it can exit
+    // its loop, update state, and schedule other command buffers.
+    kYield
   };
 
   // Return true if the given error code is an actual error.
   inline bool IsError(Error error) {
-    return (error != kNoError && error != kWaiting);
+    switch (error) {
+      case kNoError:
+      case kWaiting:
+      case kYield:
+        return false;
+      default:
+        return true;
+    }
   }
 }