mirror of
https://github.com/classilla/tenfourfox.git
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187 lines
6.1 KiB
C++
187 lines
6.1 KiB
C++
// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "base/thread_local_storage.h"
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#include <windows.h>
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#include "base/logging.h"
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// In order to make TLS destructors work, we need to keep function
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// pointers to the destructor for each TLS that we allocate.
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// We make this work by allocating a single OS-level TLS, which
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// contains an array of slots for the application to use. In
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// parallel, we also allocate an array of destructors, which we
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// keep track of and call when threads terminate.
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// tls_key_ is the one native TLS that we use. It stores our
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// table.
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long ThreadLocalStorage::tls_key_ = TLS_OUT_OF_INDEXES;
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// tls_max_ is the high-water-mark of allocated thread local storage.
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// We intentionally skip 0 so that it is not confused with an
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// unallocated TLS slot.
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long ThreadLocalStorage::tls_max_ = 1;
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// An array of destructor function pointers for the slots. If
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// a slot has a destructor, it will be stored in its corresponding
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// entry in this array.
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ThreadLocalStorage::TLSDestructorFunc
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ThreadLocalStorage::tls_destructors_[kThreadLocalStorageSize];
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void** ThreadLocalStorage::Initialize() {
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if (tls_key_ == TLS_OUT_OF_INDEXES) {
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long value = TlsAlloc();
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DCHECK(value != TLS_OUT_OF_INDEXES);
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// Atomically test-and-set the tls_key. If the key is TLS_OUT_OF_INDEXES,
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// go ahead and set it. Otherwise, do nothing, as another
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// thread already did our dirty work.
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if (InterlockedCompareExchange(&tls_key_, value, TLS_OUT_OF_INDEXES) !=
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TLS_OUT_OF_INDEXES) {
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// We've been shortcut. Another thread replaced tls_key_ first so we need
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// to destroy our index and use the one the other thread got first.
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TlsFree(value);
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}
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}
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DCHECK(TlsGetValue(tls_key_) == NULL);
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// Create an array to store our data.
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void** tls_data = new void*[kThreadLocalStorageSize];
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memset(tls_data, 0, sizeof(void*[kThreadLocalStorageSize]));
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TlsSetValue(tls_key_, tls_data);
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return tls_data;
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}
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ThreadLocalStorage::Slot::Slot(TLSDestructorFunc destructor)
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: initialized_(false) {
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Initialize(destructor);
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}
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bool ThreadLocalStorage::Slot::Initialize(TLSDestructorFunc destructor) {
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if (tls_key_ == TLS_OUT_OF_INDEXES || !TlsGetValue(tls_key_))
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ThreadLocalStorage::Initialize();
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// Grab a new slot.
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slot_ = InterlockedIncrement(&tls_max_) - 1;
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if (slot_ >= kThreadLocalStorageSize) {
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NOTREACHED();
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return false;
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}
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// Setup our destructor.
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tls_destructors_[slot_] = destructor;
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initialized_ = true;
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return true;
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}
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void ThreadLocalStorage::Slot::Free() {
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// At this time, we don't reclaim old indices for TLS slots.
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// So all we need to do is wipe the destructor.
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tls_destructors_[slot_] = NULL;
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initialized_ = false;
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}
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void* ThreadLocalStorage::Slot::Get() const {
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void** tls_data = static_cast<void**>(TlsGetValue(tls_key_));
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if (!tls_data)
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tls_data = ThreadLocalStorage::Initialize();
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DCHECK(slot_ >= 0 && slot_ < kThreadLocalStorageSize);
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return tls_data[slot_];
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}
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void ThreadLocalStorage::Slot::Set(void* value) {
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void** tls_data = static_cast<void**>(TlsGetValue(tls_key_));
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if (!tls_data)
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tls_data = ThreadLocalStorage::Initialize();
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DCHECK(slot_ >= 0 && slot_ < kThreadLocalStorageSize);
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tls_data[slot_] = value;
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}
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void ThreadLocalStorage::ThreadExit() {
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if (tls_key_ == TLS_OUT_OF_INDEXES)
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return;
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void** tls_data = static_cast<void**>(TlsGetValue(tls_key_));
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// Maybe we have never initialized TLS for this thread.
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if (!tls_data)
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return;
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for (int slot = 0; slot < tls_max_; slot++) {
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if (tls_destructors_[slot] != NULL) {
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void* value = tls_data[slot];
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tls_destructors_[slot](value);
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}
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}
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delete[] tls_data;
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// In case there are other "onexit" handlers...
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TlsSetValue(tls_key_, NULL);
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}
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// Thread Termination Callbacks.
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// Windows doesn't support a per-thread destructor with its
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// TLS primitives. So, we build it manually by inserting a
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// function to be called on each thread's exit.
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// This magic is from http://www.codeproject.com/threads/tls.asp
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// and it works for VC++ 7.0 and later.
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#ifdef _WIN64
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// This makes the linker create the TLS directory if it's not already
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// there. (e.g. if __declspec(thread) is not used).
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#pragma comment(linker, "/INCLUDE:_tls_used")
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#else // _WIN64
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// This makes the linker create the TLS directory if it's not already
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// there. (e.g. if __declspec(thread) is not used).
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#pragma comment(linker, "/INCLUDE:__tls_used")
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#endif // _WIN64
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// Static callback function to call with each thread termination.
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void NTAPI OnThreadExit(PVOID module, DWORD reason, PVOID reserved)
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{
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// On XP SP0 & SP1, the DLL_PROCESS_ATTACH is never seen. It is sent on SP2+
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// and on W2K and W2K3. So don't assume it is sent.
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if (DLL_THREAD_DETACH == reason || DLL_PROCESS_DETACH == reason)
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ThreadLocalStorage::ThreadExit();
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}
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// .CRT$XLA to .CRT$XLZ is an array of PIMAGE_TLS_CALLBACK pointers that are
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// called automatically by the OS loader code (not the CRT) when the module is
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// loaded and on thread creation. They are NOT called if the module has been
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// loaded by a LoadLibrary() call. It must have implicitly been loaded at
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// process startup.
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// By implicitly loaded, I mean that it is directly referenced by the main EXE
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// or by one of its dependent DLLs. Delay-loaded DLL doesn't count as being
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// implicitly loaded.
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//
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// See VC\crt\src\tlssup.c for reference.
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#ifdef _WIN64
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// .CRT section is merged with .rdata on x64 so it must be constant data.
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#pragma const_seg(".CRT$XLB")
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// When defining a const variable, it must have external linkage to be sure the
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// linker doesn't discard it. If this value is discarded, the OnThreadExit
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// function will never be called.
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extern const PIMAGE_TLS_CALLBACK p_thread_callback;
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const PIMAGE_TLS_CALLBACK p_thread_callback = OnThreadExit;
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// Reset the default section.
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#pragma const_seg()
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#else // _WIN64
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#pragma data_seg(".CRT$XLB")
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PIMAGE_TLS_CALLBACK p_thread_callback = OnThreadExit;
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// Reset the default section.
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#pragma data_seg()
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#endif // _WIN64
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