WTF: Initialize main-thread stack estimates when WTF starts up.

third_party/WebKit/Source/wtf/ThreadingPthreads.cpp

 /*
  * Copyright (C) 2007, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Justin Haygood (jhaygood@reaktix.com)
  * Copyright (C) 2011 Research In Motion Limited. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
@@ skipping 67 matching lines @@
 void initializeThreading() {
   // This should only be called once.
   WTFThreadData::initialize();
 
   initializeDates();
   // Force initialization of static DoubleToStringConverter converter variable
   // inside EcmaScriptConverter function while we are in single thread mode.
   double_conversion::DoubleToStringConverter::EcmaScriptConverter();
 }
 
+namespace {
+ThreadSpecificKey s_currentThreadKey;
+bool s_currentThreadKeyInitialized = false;
+}  // namespace
+
+void initializeCurrentThread() {
+  DCHECK(!s_currentThreadKeyInitialized);
+  threadSpecificKeyCreate(&s_currentThreadKey, [](void*) {});
+  s_currentThreadKeyInitialized = true;
+}
+
 ThreadIdentifier currentThread() {
-  return wtfThreadData().threadId();
+  // This doesn't use WTF::ThreadSpecific (e.g. WTFThreadData) because
+  // ThreadSpecific now depends on currentThread. It is necessary to avoid this
+  // or a similar loop:
+  //
+  // currentThread
+  // -> wtfThreadData
+  // -> ThreadSpecific::operator*
+  // -> isMainThread
+  // -> currentThread
+  static_assert(sizeof(ThreadIdentifier) <= sizeof(void*),
+                "ThreadIdentifier must fit in a void*.");
+  DCHECK(s_currentThreadKeyInitialized);
+  void* value = threadSpecificGet(s_currentThreadKey);
+  if (UNLIKELY(!value)) {
+    value = reinterpret_cast<void*>(
+        static_cast<intptr_t>(internal::currentThreadSyscall()));
+    DCHECK(value);
+    threadSpecificSet(s_currentThreadKey, value);
+  }
+  return reinterpret_cast<intptr_t>(threadSpecificGet(s_currentThreadKey));
 }
 
 MutexBase::MutexBase(bool recursive) {
   pthread_mutexattr_t attr;
   pthread_mutexattr_init(&attr);
   pthread_mutexattr_settype(
       &attr, recursive ? PTHREAD_MUTEX_RECURSIVE : PTHREAD_MUTEX_NORMAL);
 
   int result = pthread_mutex_init(&m_mutex.m_internalMutex, &attr);
   DCHECK_EQ(result, 0);
@@ skipping 124 matching lines @@
 }
 
 void willCreateThread() {
   s_threadCreated = true;
 }
 #endif
 
 }  // namespace WTF
 
 #endif  // OS(POSIX)