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authorinitial.commit <initial.commit@0039d316-1c4b-4281-b951-d872f2087c98>2008-07-26 21:49:38 +0000
committerinitial.commit <initial.commit@0039d316-1c4b-4281-b951-d872f2087c98>2008-07-26 21:49:38 +0000
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git-svn-id: svn://svn.chromium.org/chrome/trunk/src@8 0039d316-1c4b-4281-b951-d872f2087c98
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+// Copyright 2008, 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
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+// * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <windows.h>
+
+#include "base/thread_local_storage.h"
+
+#include "base/logging.h"
+
+// In order to make TLS destructors work, we need to keep function
+// pointers to the destructor for each TLS that we allocate.
+// We make this work by allocating a single OS-level TLS, which
+// contains an array of slots for the application to use. In
+// parallel, we also allocate an array of destructors, which we
+// keep track of and call when threads terminate.
+
+// tls_key_ is the one native TLS that we use. It stores our
+// table.
+long ThreadLocalStorage::tls_key_ = TLS_OUT_OF_INDEXES;
+
+// tls_max_ is the high-water-mark of allocated thread local storage.
+// We intentionally skip 0 so that it is not confused with an
+// unallocated TLS slot.
+long ThreadLocalStorage::tls_max_ = 1;
+
+// An array of destructor function pointers for the slots. If
+// a slot has a destructor, it will be stored in its corresponding
+// entry in this array.
+ThreadLocalStorage::TLSDestructorFunc
+ ThreadLocalStorage::tls_destructors_[kThreadLocalStorageSize];
+
+void **ThreadLocalStorage::Initialize() {
+ if (tls_key_ == TLS_OUT_OF_INDEXES) {
+ long value = TlsAlloc();
+ DCHECK(value != TLS_OUT_OF_INDEXES);
+
+ // Atomically test-and-set the tls_key. If the key is TLS_OUT_OF_INDEXES,
+ // go ahead and set it. Otherwise, do nothing, as another
+ // thread already did our dirty work.
+ if (InterlockedCompareExchange(&tls_key_, value, TLS_OUT_OF_INDEXES) !=
+ TLS_OUT_OF_INDEXES) {
+ // We've been shortcut. Another thread replaced tls_key_ first so we need
+ // to destroy our index and use the one the other thread got first.
+ TlsFree(value);
+ }
+ }
+ DCHECK(TlsGetValue(tls_key_) == NULL);
+
+ // Create an array to store our data.
+ void **tls_data = new void*[kThreadLocalStorageSize];
+ memset(tls_data, 0, sizeof(void*[kThreadLocalStorageSize]));
+ TlsSetValue(tls_key_, tls_data);
+ return tls_data;
+}
+
+TLSSlot ThreadLocalStorage::Alloc(TLSDestructorFunc destructor) {
+ if (tls_key_ == TLS_OUT_OF_INDEXES || !TlsGetValue(tls_key_))
+ Initialize();
+
+ // Grab a new slot.
+ int slot = InterlockedIncrement(&tls_max_) - 1;
+ if (slot >= kThreadLocalStorageSize) {
+ NOTREACHED();
+ return -1;
+ }
+
+ // Setup our destructor.
+ tls_destructors_[slot] = destructor;
+ return slot;
+}
+
+void ThreadLocalStorage::Free(TLSSlot slot) {
+ // At this time, we don't reclaim old indices for TLS slots.
+ // So all we need to do is wipe the destructor.
+ tls_destructors_[slot] = NULL;
+}
+
+void* ThreadLocalStorage::Get(TLSSlot slot) {
+ void **tls_data = static_cast<void**>(TlsGetValue(tls_key_));
+ if (!tls_data)
+ tls_data = Initialize();
+ DCHECK(slot >= 0 && slot < kThreadLocalStorageSize);
+ return tls_data[slot];
+}
+
+void ThreadLocalStorage::Set(TLSSlot slot, void* value) {
+ void **tls_data = static_cast<void**>(TlsGetValue(tls_key_));
+ if (!tls_data)
+ tls_data = Initialize();
+ DCHECK(slot >= 0 && slot < kThreadLocalStorageSize);
+ tls_data[slot] = value;
+}
+
+void ThreadLocalStorage::ThreadExit() {
+ void **tls_data = static_cast<void**>(TlsGetValue(tls_key_));
+
+ // Maybe we have never initialized TLS for this thread.
+ if (!tls_data)
+ return;
+
+ for (int slot = 0; slot < tls_max_; slot++) {
+ if (tls_destructors_[slot] != NULL) {
+ void *value = tls_data[slot];
+ tls_destructors_[slot](value);
+ }
+ }
+
+ delete[] tls_data;
+
+ // In case there are other "onexit" handlers...
+ TlsSetValue(tls_key_, NULL);
+}
+
+// Thread Termination Callbacks.
+// Windows doesn't support a per-thread destructor with its
+// TLS primitives. So, we build it manually by inserting a
+// function to be called on each thread's exit.
+// This magic is from http://www.codeproject.com/threads/tls.asp
+// and it works for VC++ 7.0 and later.
+
+// This makes the linker create the TLS directory if it's not already
+// there. (e.g. if __declspec(thread) is not used).
+#pragma comment(linker, "/INCLUDE:__tls_used")
+
+// Static callback function to call with each thread termination.
+void NTAPI OnThreadExit(PVOID module, DWORD reason, PVOID reserved)
+{
+ // On XP SP0 & SP1, the DLL_PROCESS_ATTACH is never seen. It is sent on SP2+
+ // and on W2K and W2K3. So don't assume it is sent.
+ if (DLL_THREAD_DETACH == reason || DLL_PROCESS_DETACH == reason)
+ ThreadLocalStorage::ThreadExit();
+}
+
+// Note: .CRT section get merged with .rdata on x64 so it should be constant
+// data.
+//
+// .CRT$XLA to .CRT$XLZ is an array of PIMAGE_TLS_CALLBACK pointers that are
+// called automatically by the OS loader code (not the CRT) when the module is
+// loaded and on thread creation. They are NOT called if the module has been
+// loaded by a LoadLibrary() call. It must have implicitly been loaded at
+// process startup.
+// By implicitly loaded, I mean that it is directly referenced by the main EXE
+// or by one of its dependent DLLs. Delay-loaded DLL doesn't count as being
+// implicitly loaded.
+//
+// See VC\crt\src\tlssup.c for reference.
+#pragma data_seg(".CRT$XLB")
+PIMAGE_TLS_CALLBACK p_thread_callback = OnThreadExit;
+
+// Reset the default section.
+#pragma data_seg()
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