1/* Implementation of W32-specific threads compatibility routines for 2 libgcc2. */ 3 4/* Copyright (C) 1999-2022 Free Software Foundation, Inc. 5 Contributed by Mumit Khan <khan@xraylith.wisc.edu>. 6 Modified and moved to separate file by Danny Smith 7 <dannysmith@users.sourceforge.net>. 8 9This file is part of GCC. 10 11GCC is free software; you can redistribute it and/or modify it under 12the terms of the GNU General Public License as published by the Free 13Software Foundation; either version 3, or (at your option) any later 14version. 15 16GCC is distributed in the hope that it will be useful, but WITHOUT ANY 17WARRANTY; without even the implied warranty of MERCHANTABILITY or 18FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 19for more details. 20 21Under Section 7 of GPL version 3, you are granted additional 22permissions described in the GCC Runtime Library Exception, version 233.1, as published by the Free Software Foundation. 24 25You should have received a copy of the GNU General Public License and 26a copy of the GCC Runtime Library Exception along with this program; 27see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 28<http://www.gnu.org/licenses/>. */ 29 30#include <windows.h> 31#ifndef __GTHREAD_HIDE_WIN32API 32# define __GTHREAD_HIDE_WIN32API 1 33#endif 34#include "gthr-win32.h" 35 36/* Windows32 threads specific definitions. The windows32 threading model 37 does not map well into pthread-inspired gcc's threading model, and so 38 there are caveats one needs to be aware of. 39 40 1. The destructor supplied to __gthread_key_create is ignored for 41 generic x86-win32 ports. This will certainly cause memory leaks 42 due to unreclaimed eh contexts (sizeof (eh_context) is at least 43 24 bytes for x86 currently). 44 45 This memory leak may be significant for long-running applications 46 that make heavy use of C++ EH. 47 48 However, Mingw runtime (version 0.3 or newer) provides a mechanism 49 to emulate pthreads key dtors; the runtime provides a special DLL, 50 linked in if -mthreads option is specified, that runs the dtors in 51 the reverse order of registration when each thread exits. If 52 -mthreads option is not given, a stub is linked in instead of the 53 DLL, which results in memory leak. Other x86-win32 ports can use 54 the same technique of course to avoid the leak. 55 56 2. The error codes returned are non-POSIX like, and cast into ints. 57 This may cause incorrect error return due to truncation values on 58 hw where sizeof (DWORD) > sizeof (int). 59 60 3. We are currently using a special mutex instead of the Critical 61 Sections, since Win9x does not support TryEnterCriticalSection 62 (while NT does). 63 64 The basic framework should work well enough. In the long term, GCC 65 needs to use Structured Exception Handling on Windows32. */ 66 67int 68__gthr_win32_once (__gthread_once_t *once, void (*func) (void)) 69{ 70 if (once == NULL || func == NULL) 71 return EINVAL; 72 73 if (! once->done) 74 { 75 if (InterlockedIncrement (&(once->started)) == 0) 76 { 77 (*func) (); 78 once->done = TRUE; 79 } 80 else 81 { 82 /* Another thread is currently executing the code, so wait for it 83 to finish; yield the CPU in the meantime. If performance 84 does become an issue, the solution is to use an Event that 85 we wait on here (and set above), but that implies a place to 86 create the event before this routine is called. */ 87 while (! once->done) 88 Sleep (0); 89 } 90 } 91 return 0; 92} 93 94/* Windows32 thread local keys don't support destructors; this leads to 95 leaks, especially in threaded applications making extensive use of 96 C++ EH. Mingw uses a thread-support DLL to work-around this problem. */ 97 98int 99__gthr_win32_key_create (__gthread_key_t *key, 100 void (*dtor) (void *) __attribute__((unused))) 101{ 102 int status = 0; 103 DWORD tls_index = TlsAlloc (); 104 if (tls_index != 0xFFFFFFFF) 105 { 106 *key = tls_index; 107#ifdef MINGW32_SUPPORTS_MT_EH 108 /* Mingw runtime will run the dtors in reverse order for each thread 109 when the thread exits. */ 110 status = __mingwthr_key_dtor (*key, dtor); 111#endif 112 } 113 else 114 status = (int) GetLastError (); 115 return status; 116} 117 118int 119__gthr_win32_key_delete (__gthread_key_t key) 120{ 121 return (TlsFree (key) != 0) ? 0 : (int) GetLastError (); 122} 123 124void * 125__gthr_win32_getspecific (__gthread_key_t key) 126{ 127 DWORD lasterror; 128 void *ptr; 129 lasterror = GetLastError(); 130 ptr = TlsGetValue(key); 131 SetLastError( lasterror ); 132 return ptr; 133} 134 135int 136__gthr_win32_setspecific (__gthread_key_t key, const void *ptr) 137{ 138 if (TlsSetValue (key, CONST_CAST2(void *, const void *, ptr)) != 0) 139 return 0; 140 else 141 return GetLastError (); 142} 143 144void 145__gthr_win32_mutex_init_function (__gthread_mutex_t *mutex) 146{ 147 mutex->counter = -1; 148 mutex->sema = CreateSemaphoreW (NULL, 0, 65535, NULL); 149} 150 151void 152__gthr_win32_mutex_destroy (__gthread_mutex_t *mutex) 153{ 154 CloseHandle ((HANDLE) mutex->sema); 155} 156 157int 158__gthr_win32_mutex_lock (__gthread_mutex_t *mutex) 159{ 160 if (InterlockedIncrement (&mutex->counter) == 0 || 161 WaitForSingleObject (mutex->sema, INFINITE) == WAIT_OBJECT_0) 162 return 0; 163 else 164 { 165 /* WaitForSingleObject returns WAIT_FAILED, and we can only do 166 some best-effort cleanup here. */ 167 InterlockedDecrement (&mutex->counter); 168 return 1; 169 } 170} 171 172int 173__gthr_win32_mutex_trylock (__gthread_mutex_t *mutex) 174{ 175 if (__GTHR_W32_InterlockedCompareExchange (&mutex->counter, 0, -1) < 0) 176 return 0; 177 else 178 return 1; 179} 180 181int 182__gthr_win32_mutex_unlock (__gthread_mutex_t *mutex) 183{ 184 if (InterlockedDecrement (&mutex->counter) >= 0) 185 return ReleaseSemaphore (mutex->sema, 1, NULL) ? 0 : 1; 186 else 187 return 0; 188} 189 190void 191__gthr_win32_recursive_mutex_init_function (__gthread_recursive_mutex_t *mutex) 192{ 193 mutex->counter = -1; 194 mutex->depth = 0; 195 mutex->owner = 0; 196 mutex->sema = CreateSemaphoreW (NULL, 0, 65535, NULL); 197} 198 199int 200__gthr_win32_recursive_mutex_lock (__gthread_recursive_mutex_t *mutex) 201{ 202 DWORD me = GetCurrentThreadId(); 203 if (InterlockedIncrement (&mutex->counter) == 0) 204 { 205 mutex->depth = 1; 206 mutex->owner = me; 207 } 208 else if (mutex->owner == me) 209 { 210 InterlockedDecrement (&mutex->counter); 211 ++(mutex->depth); 212 } 213 else if (WaitForSingleObject (mutex->sema, INFINITE) == WAIT_OBJECT_0) 214 { 215 mutex->depth = 1; 216 mutex->owner = me; 217 } 218 else 219 { 220 /* WaitForSingleObject returns WAIT_FAILED, and we can only do 221 some best-effort cleanup here. */ 222 InterlockedDecrement (&mutex->counter); 223 return 1; 224 } 225 return 0; 226} 227 228int 229__gthr_win32_recursive_mutex_trylock (__gthread_recursive_mutex_t *mutex) 230{ 231 DWORD me = GetCurrentThreadId(); 232 if (__GTHR_W32_InterlockedCompareExchange (&mutex->counter, 0, -1) < 0) 233 { 234 mutex->depth = 1; 235 mutex->owner = me; 236 } 237 else if (mutex->owner == me) 238 ++(mutex->depth); 239 else 240 return 1; 241 242 return 0; 243} 244 245int 246__gthr_win32_recursive_mutex_unlock (__gthread_recursive_mutex_t *mutex) 247{ 248 --(mutex->depth); 249 if (mutex->depth == 0) 250 { 251 mutex->owner = 0; 252 253 if (InterlockedDecrement (&mutex->counter) >= 0) 254 return ReleaseSemaphore (mutex->sema, 1, NULL) ? 0 : 1; 255 } 256 257 return 0; 258} 259 260int 261__gthr_win32_recursive_mutex_destroy (__gthread_recursive_mutex_t *mutex) 262{ 263 CloseHandle ((HANDLE) mutex->sema); 264 return 0; 265} 266