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