1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include "base/threading/thread_local_storage.h" 6 7 #include <windows.h> 8 9 #include "base/logging.h" 10 11 namespace base { 12 13 namespace internal { 14 15 bool PlatformThreadLocalStorage::AllocTLS(TLSKey* key) { 16 TLSKey value = TlsAlloc(); 17 if (value != TLS_OUT_OF_INDEXES) { 18 *key = value; 19 return true; 20 } 21 return false; 22 } 23 24 void PlatformThreadLocalStorage::FreeTLS(TLSKey key) { 25 BOOL ret = TlsFree(key); 26 DCHECK(ret); 27 } 28 29 void* PlatformThreadLocalStorage::GetTLSValue(TLSKey key) { 30 return TlsGetValue(key); 31 } 32 33 void PlatformThreadLocalStorage::SetTLSValue(TLSKey key, void* value) { 34 BOOL ret = TlsSetValue(key, value); 35 DCHECK(ret); 36 } 37 38 } // namespace internal 39 40 } // namespace base 41 42 // Thread Termination Callbacks. 43 // Windows doesn't support a per-thread destructor with its 44 // TLS primitives. So, we build it manually by inserting a 45 // function to be called on each thread's exit. 46 // This magic is from http://www.codeproject.com/threads/tls.asp 47 // and it works for VC++ 7.0 and later. 48 49 // Force a reference to _tls_used to make the linker create the TLS directory 50 // if it's not already there. (e.g. if __declspec(thread) is not used). 51 // Force a reference to p_thread_callback_base to prevent whole program 52 // optimization from discarding the variable. 53 #ifdef _WIN64 54 55 #pragma comment(linker, "/INCLUDE:_tls_used") 56 #pragma comment(linker, "/INCLUDE:p_thread_callback_base") 57 58 #else // _WIN64 59 60 #pragma comment(linker, "/INCLUDE:__tls_used") 61 #pragma comment(linker, "/INCLUDE:_p_thread_callback_base") 62 63 #endif // _WIN64 64 65 // Static callback function to call with each thread termination. 66 void NTAPI OnThreadExit(PVOID module, DWORD reason, PVOID reserved) { 67 // On XP SP0 & SP1, the DLL_PROCESS_ATTACH is never seen. It is sent on SP2+ 68 // and on W2K and W2K3. So don't assume it is sent. 69 if (DLL_THREAD_DETACH == reason || DLL_PROCESS_DETACH == reason) 70 base::internal::PlatformThreadLocalStorage::OnThreadExit(); 71 } 72 73 // .CRT$XLA to .CRT$XLZ is an array of PIMAGE_TLS_CALLBACK pointers that are 74 // called automatically by the OS loader code (not the CRT) when the module is 75 // loaded and on thread creation. They are NOT called if the module has been 76 // loaded by a LoadLibrary() call. It must have implicitly been loaded at 77 // process startup. 78 // By implicitly loaded, I mean that it is directly referenced by the main EXE 79 // or by one of its dependent DLLs. Delay-loaded DLL doesn't count as being 80 // implicitly loaded. 81 // 82 // See VC\crt\src\tlssup.c for reference. 83 84 // extern "C" suppresses C++ name mangling so we know the symbol name for the 85 // linker /INCLUDE:symbol pragma above. 86 extern "C" { 87 // The linker must not discard p_thread_callback_base. (We force a reference 88 // to this variable with a linker /INCLUDE:symbol pragma to ensure that.) If 89 // this variable is discarded, the OnThreadExit function will never be called. 90 #ifdef _WIN64 91 92 // .CRT section is merged with .rdata on x64 so it must be constant data. 93 #pragma const_seg(".CRT$XLB") 94 // When defining a const variable, it must have external linkage to be sure the 95 // linker doesn't discard it. 96 extern const PIMAGE_TLS_CALLBACK p_thread_callback_base; 97 const PIMAGE_TLS_CALLBACK p_thread_callback_base = OnThreadExit; 98 99 // Reset the default section. 100 #pragma const_seg() 101 102 #else // _WIN64 103 104 #pragma data_seg(".CRT$XLB") 105 PIMAGE_TLS_CALLBACK p_thread_callback_base = OnThreadExit; 106 107 // Reset the default section. 108 #pragma data_seg() 109 110 #endif // _WIN64 111 } // extern "C" 112
