cc: Prevent recursion in *TileTaskWorkerPool methods.

cc/base/util.h

Index: cc/base/util.h
diff --git a/cc/base/util.h b/cc/base/util.h
index 1d716ae2a42f4b4d25f1bf38e6fb38a4a9c806a3..03eda4572375cadbe8f1b2d07b2d2ee4f52c5044 100644
--- a/cc/base/util.h
+++ b/cc/base/util.h
@@ -8,6 +8,7 @@
 #include <limits>
 
 #include "base/basictypes.h"
+#include "base/logging.h"
 
 namespace cc {
 
@@ -24,6 +25,23 @@ template <typename T> T RoundDown(T n, T mul) {
                  : ((n - mul + 1) / mul) * mul;
 }
 
+class ScopedSingleEntry {

[reveman, 2014/12/18 19:24:07]

This seems very similar to base::ThreadCollisionWarner. I guess you could just
use that instead but that might be confusing as it's not really checking for
thread collisions. Would be nice if usage was at least consistent with
base::ThreadCollisionWarner..

[vmiura, 2014/12/18 21:16:48]

DFAKE_SCOPED_LOCK() seems like a superset of what we need; it detects recursion,
as well as multiple thread entry.  Would you be OK if I use that?

The failure looks like:

[40382:40383:1218/131159:763931716939:FATAL:thread_collision_warner.cc(13)]
Check failed: false. Thread Collision
#0 0x0000010f55fe base::debug::StackTrace::StackTrace()
#1 0x00000113c6b5 logging::LogMessage::~LogMessage()
#2 0x0000011c40e1 base::DCheckAsserter::warn()
#3 0x0000011c41f6 base::ThreadCollisionWarner::Enter()
#4 0x000000ef76a3 base::ThreadCollisionWarner::ScopedCheck::ScopedCheck()
#5 0x000000ef5fa4 cc::PixelBufferTileTaskWorkerPool::CheckForCompletedTasks()
#6 0x000000ef64ac cc::PixelBufferTileTaskWorkerPool::CheckForCompletedTasks()
#7 0x000000f68297 cc::TileManager::CheckIfMoreTilesNeedPrepare()
#8 0x000000f69209 cc::TileManager::DidFinishRunningTileTasks()
#9 0x000000ef0ebc
cc::PixelBufferTileTaskWorkerPool::CheckForCompletedRasterTasks()
#10 0x000000ef689c cc::PixelBufferTileTaskWorkerPool::OnTaskSetFinished()
#11 0x000000b62eda base::internal::RunnableAdapter<>::Run()
#12 0x000000ea20d8 base::internal::InvokeHelper<>::MakeItSo()
#13 0x000000efc88c base::internal::Invoker<>::Run()
#14 0x0000004e376e base::Callback<>::Run()

[reveman, 2014/12/19 00:03:18]

Yes, I think that's better than adding this new class. Ideally we'd have
something called a ReentryChecker in base but if ThreadCollisionWarner works I
think it's a good idea to just use that. This is only for
PixelBufferTileTaskWorkerPool, which we'll hopefully be able to remove soon
anyhow.

+ public:
+  explicit ScopedSingleEntry(bool* single_entry_holder)
+      : single_entry_holder_(single_entry_holder) {
+    DCHECK(!*single_entry_holder_);
+    *single_entry_holder_ = true;
+  }
+
+  ~ScopedSingleEntry() {
+    DCHECK(*single_entry_holder_);
+    *single_entry_holder_ = false;
+  }
+
+ private:
+  bool* single_entry_holder_;
+};
+
 }  // namespace cc
 
 #endif  // CC_BASE_UTIL_H_