thread_local_storage_win.cc (3493B)
1 // Copyright 2012 The Chromium Authors 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/check.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::SetTLSValue(TLSKey key, void* value) { 30 BOOL ret = TlsSetValue(key, value); 31 DCHECK(ret); 32 } 33 34 } // namespace internal 35 36 } // namespace base 37 38 // Thread Termination Callbacks. 39 // Windows doesn't support a per-thread destructor with its 40 // TLS primitives. So, we build it manually by inserting a 41 // function to be called on each thread's exit. 42 // This magic is from http://www.codeproject.com/threads/tls.asp 43 // and it works for VC++ 7.0 and later. 44 45 // Force a reference to _tls_used to make the linker create the TLS directory 46 // if it's not already there. (e.g. if __declspec(thread) is not used). 47 // Force a reference to p_thread_callback_base to prevent whole program 48 // optimization from discarding the variable. 49 #ifdef _WIN64 50 51 #pragma comment(linker, "/INCLUDE:_tls_used") 52 #pragma comment(linker, "/INCLUDE:p_thread_callback_base") 53 54 #else // _WIN64 55 56 #pragma comment(linker, "/INCLUDE:__tls_used") 57 #pragma comment(linker, "/INCLUDE:_p_thread_callback_base") 58 59 #endif // _WIN64 60 61 // Static callback function to call with each thread termination. 62 void NTAPI OnThreadExit(PVOID module, DWORD reason, PVOID reserved) { 63 // On XP SP0 & SP1, the DLL_PROCESS_ATTACH is never seen. It is sent on SP2+ 64 // and on W2K and W2K3. So don't assume it is sent. 65 if (DLL_THREAD_DETACH == reason || DLL_PROCESS_DETACH == reason) 66 base::internal::PlatformThreadLocalStorage::OnThreadExit(); 67 } 68 69 // .CRT$XLA to .CRT$XLZ is an array of PIMAGE_TLS_CALLBACK pointers that are 70 // called automatically by the OS loader code (not the CRT) when the module is 71 // loaded and on thread creation. They are NOT called if the module has been 72 // loaded by a LoadLibrary() call. It must have implicitly been loaded at 73 // process startup. 74 // By implicitly loaded, I mean that it is directly referenced by the main EXE 75 // or by one of its dependent DLLs. Delay-loaded DLL doesn't count as being 76 // implicitly loaded. 77 // 78 // See VC\crt\src\tlssup.c for reference. 79 80 // extern "C" suppresses C++ name mangling so we know the symbol name for the 81 // linker /INCLUDE:symbol pragma above. 82 extern "C" { 83 // The linker must not discard p_thread_callback_base. (We force a reference 84 // to this variable with a linker /INCLUDE:symbol pragma to ensure that.) If 85 // this variable is discarded, the OnThreadExit function will never be called. 86 #ifdef _WIN64 87 88 // .CRT section is merged with .rdata on x64 so it must be constant data. 89 #pragma const_seg(".CRT$XLB") 90 // When defining a const variable, it must have external linkage to be sure the 91 // linker doesn't discard it. 92 extern const PIMAGE_TLS_CALLBACK p_thread_callback_base; 93 const PIMAGE_TLS_CALLBACK p_thread_callback_base = OnThreadExit; 94 95 // Reset the default section. 96 #pragma const_seg() 97 98 #else // _WIN64 99 100 #pragma data_seg(".CRT$XLB") 101 PIMAGE_TLS_CALLBACK p_thread_callback_base = OnThreadExit; 102 103 // Reset the default section. 104 #pragma data_seg() 105 106 #endif // _WIN64 107 } // extern "C"