Oilpan: Avoid looking up TLS in ThreadState::current()

Source/platform/heap/ThreadState.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 92 matching lines @@
 #ifdef _WIN64
     return reinterpret_cast<void*>(__readgsqword(offsetof(NT_TIB64, StackBase)));
 #else
     return reinterpret_cast<void*>(__readfsdword(offsetof(NT_TIB, StackBase)));
 #endif
 #else
 #error Unsupported getStackStart on this platform.
 #endif
 }
 
+static size_t getStackSize()
+{
+#if defined(__GLIBC__) || OS(ANDROID) || OS(FREEBSD)
+    // We cannot get the stack size in these platforms because
+    // pthread_getattr_np() can fail for the main thread.
+    // It is OK to return 0 because ThreadState::current() doesn't use
+    // the stack size in these platforms.
+    return 0;
+#elif OS(MACOSX)
+    return pthread_get_stacksize_np(pthread_self());
+#elif OS(WIN) && COMPILER(MSVC)
+    // On Windows stack limits for the current thread are available in
+    // the thread information block (TIB). Its fields can be accessed through
+    // FS segment register on x86 and GS segment register on x86_64.
+#ifdef _WIN64
+    return __readgsqword(offsetof(NT_TIB64, StackBase)) - __readgsqword(offsetof(NT_TIB64, StackLimit));

[sof, 2014/10/12 08:09:23]

Does this account for stack usage&sizes exceeding the initial commit, i.e.,
won't StackLimit grow as the guard page is hit and more is committed?

(This comment really belongs at the getStackSize() call site, I suppose.)

[haraken, 2014/10/12 08:45:49]

I don't know if the StackLimit grows up dynamically.

Given that the stack pointer check is a best-effort service, it is OK to
underestimate the stack size. I renamed the method to
getUnderestimatedStackSize().

However, I welcome a better solution.

[sof, 2014/10/12 11:39:16]

Yes, if the initial commit is 1M, then calling current() with a deeper stack
ought to be rare (a guess), so not having it track the current stack limit/size
seems just fine.

+#else
+    return __readfsdword(offsetof(NT_TIB, StackBase)) - __readfsdword(offsetof(NT_TIB, StackLimit));
+#endif
+#else
+#error Unsupported getStackSize on this platform.
+#endif
+}
+
 // The maximum number of WrapperPersistentRegions to keep around in the
 // m_pooledWrapperPersistentRegions pool.
 static const size_t MaxPooledWrapperPersistentRegionCount = 2;
 
 WTF::ThreadSpecific<ThreadState*>* ThreadState::s_threadSpecific = 0;
+intptr_t ThreadState::s_mainThreadStackStart = 0;
+intptr_t ThreadState::s_mainThreadStackSize = 0;
 uint8_t ThreadState::s_mainThreadStateStorage[sizeof(ThreadState)];
 SafePointBarrier* ThreadState::s_safePointBarrier = 0;
 bool ThreadState::s_inGC = false;
 
 static Mutex& threadAttachMutex()
 {
     AtomicallyInitializedStatic(Mutex&, mutex = *new Mutex);
     return mutex;
 }
 
@@ skipping 190 matching lines @@
     , m_shouldFlushHeapDoesNotContainCache(false)
     , m_lowCollectionRate(false)
     , m_numberOfSweeperTasks(0)
 #if defined(ADDRESS_SANITIZER)
     , m_asanFakeStack(__asan_get_current_fake_stack())
 #endif
 {
     ASSERT(!**s_threadSpecific);
     **s_threadSpecific = this;
 
+    if (isMainThread()) {
+        s_mainThreadStackStart = reinterpret_cast<intptr_t>(m_startOfStack);
+        s_mainThreadStackSize = getStackSize();
+    }
+
     InitializeHeaps<NumberOfHeaps>::init(m_heaps, this);
 
     m_weakCallbackStack = new CallbackStack();
 
     if (blink::Platform::current())
         m_sweeperThread = adoptPtr(blink::Platform::current()->createThread("Blink GC Sweeper"));
 }
 
 ThreadState::~ThreadState()
 {
@@ skipping 944 matching lines @@
             return gcInfo;
         }
     }
     if (needLockForIteration)
         threadAttachMutex().unlock();
     return 0;
 }
 #endif
 
 }