gcc/config/i386/gthr-win32.c

   1 /* Implementation of W32-specific threads compatibility routines for
   2    libgcc2.  */
   3
   4 /* Copyright (C) 1999, 2000, 2002, 2004, 2008 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
   9 This file is part of GCC.
  10
  11 GCC is free software; you can redistribute it and/or modify it under
  12 the terms of the GNU General Public License as published by the Free
  13 Software Foundation; either version 2, or (at your option) any later
  14 version.
  15
  16 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  17 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  18 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  19 for more details.
  20
  21 You should have received a copy of the GNU General Public License
  22 along with GCC; see the file COPYING.  If not, write to the Free
  23 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
  24 02110-1301, USA.  */
  25
  26 /* As a special exception, if you link this library with other files,
  27    some of which are compiled with GCC, to produce an executable,
  28    this library does not by itself cause the resulting executable
  29    to be covered by the GNU General Public License.
  30    This exception does not however invalidate any other reasons why
  31    the executable file might be covered by the GNU General Public License.  */
  32
  33
  34 #include <windows.h>
  35 #ifndef __GTHREAD_HIDE_WIN32API
  36 # define __GTHREAD_HIDE_WIN32API 1
  37 #endif
  38 #undef  __GTHREAD_I486_INLINE_LOCK_PRIMITIVES
  39 #define __GTHREAD_I486_INLINE_LOCK_PRIMITIVES
  40 #include <gthr-win32.h>
  41
  42 /* Windows32 threads specific definitions. The windows32 threading model
  43    does not map well into pthread-inspired gcc's threading model, and so
  44    there are caveats one needs to be aware of.
  45
  46    1. The destructor supplied to __gthread_key_create is ignored for
  47       generic x86-win32 ports. This will certainly cause memory leaks
  48       due to unreclaimed eh contexts (sizeof (eh_context) is at least
  49       24 bytes for x86 currently).
  50
  51       This memory leak may be significant for long-running applications
  52       that make heavy use of C++ EH.
  53
  54       However, Mingw runtime (version 0.3 or newer) provides a mechanism
  55       to emulate pthreads key dtors; the runtime provides a special DLL,
  56       linked in if -mthreads option is specified, that runs the dtors in
  57       the reverse order of registration when each thread exits. If
  58       -mthreads option is not given, a stub is linked in instead of the
  59       DLL, which results in memory leak. Other x86-win32 ports can use
  60       the same technique of course to avoid the leak.
  61
  62    2. The error codes returned are non-POSIX like, and cast into ints.
  63       This may cause incorrect error return due to truncation values on
  64       hw where sizeof (DWORD) > sizeof (int).
  65
  66    3. We are currently using a special mutex instead of the Critical
  67       Sections, since Win9x does not support TryEnterCriticalSection
  68       (while NT does).
  69
  70    The basic framework should work well enough. In the long term, GCC
  71    needs to use Structured Exception Handling on Windows32.  */
  72
  73 int
  74 __gthr_win32_once (__gthread_once_t *once, void (*func) (void))
  75 {
  76   if (once == NULL || func == NULL)
  77     return EINVAL;
  78
  79   if (! once->done)
  80     {
  81       if (InterlockedIncrement (&(once->started)) == 0)
  82         {
  83           (*func) ();
  84           once->done = TRUE;
  85         }
  86       else
  87         {
  88           /* Another thread is currently executing the code, so wait for it
  89              to finish; yield the CPU in the meantime.  If performance
  90              does become an issue, the solution is to use an Event that
  91              we wait on here (and set above), but that implies a place to
  92              create the event before this routine is called.  */
  93           while (! once->done)
  94             Sleep (0);
  95         }
  96     }
  97   return 0;
  98 }
  99
 100 /* Windows32 thread local keys don't support destructors; this leads to
 101    leaks, especially in threaded applications making extensive use of
 102    C++ EH. Mingw uses a thread-support DLL to work-around this problem.  */
 103
 104 int
 105 __gthr_win32_key_create (__gthread_key_t *key,
 106                          void (*dtor) (void *) __attribute__((unused)))
 107 {
 108   int status = 0;
 109   DWORD tls_index = TlsAlloc ();
 110   if (tls_index != 0xFFFFFFFF)
 111     {
 112       *key = tls_index;
 113 #ifdef MINGW32_SUPPORTS_MT_EH
 114       /* Mingw runtime will run the dtors in reverse order for each thread
 115          when the thread exits.  */
 116       status = __mingwthr_key_dtor (*key, dtor);
 117 #endif
 118     }
 119   else
 120     status = (int) GetLastError ();
 121   return status;
 122 }
 123
 124 int
 125 __gthr_win32_key_delete (__gthread_key_t key)
 126 {
 127   return (TlsFree (key) != 0) ? 0 : (int) GetLastError ();
 128 }
 129
 130 void *
 131 __gthr_win32_getspecific (__gthread_key_t key)
 132 {
 133   DWORD lasterror;
 134   void *ptr;
 135   lasterror = GetLastError();
 136   ptr = TlsGetValue(key);
 137   SetLastError( lasterror );
 138   return ptr;
 139 }
 140
 141 int
 142 __gthr_win32_setspecific (__gthread_key_t key, const void *ptr)
 143 {
 144   if (TlsSetValue (key, CONST_CAST2(void *, const void *, ptr)) != 0)
 145     return 0;
 146   else
 147     return GetLastError ();
 148 }
 149
 150 void
 151 __gthr_win32_mutex_init_function (__gthread_mutex_t *mutex)
 152 {
 153   mutex->counter = -1;
 154   mutex->sema = CreateSemaphore (NULL, 0, 65535, NULL);
 155 }
 156
 157 void
 158 __gthr_win32_mutex_destroy (__gthread_mutex_t *mutex)
 159 {
 160   CloseHandle ((HANDLE) mutex->sema);
 161 }
 162
 163 int
 164 __gthr_win32_mutex_lock (__gthread_mutex_t *mutex)
 165 {
 166   if (InterlockedIncrement (&mutex->counter) == 0 ||
 167       WaitForSingleObject (mutex->sema, INFINITE) == WAIT_OBJECT_0)
 168     return 0;
 169   else
 170     {
 171       /* WaitForSingleObject returns WAIT_FAILED, and we can only do
 172          some best-effort cleanup here.  */
 173       InterlockedDecrement (&mutex->counter);
 174       return 1;
 175     }
 176 }
 177
 178 int
 179 __gthr_win32_mutex_trylock (__gthread_mutex_t *mutex)
 180 {
 181   if (__GTHR_W32_InterlockedCompareExchange (&mutex->counter, 0, -1) < 0)
 182     return 0;
 183   else
 184     return 1;
 185 }
 186
 187 int
 188 __gthr_win32_mutex_unlock (__gthread_mutex_t *mutex)
 189 {
 190   if (InterlockedDecrement (&mutex->counter) >= 0)
 191     return ReleaseSemaphore (mutex->sema, 1, NULL) ? 0 : 1;
 192   else
 193     return 0;
 194 }
 195
 196 void
 197 __gthr_win32_recursive_mutex_init_function (__gthread_recursive_mutex_t *mutex)
 198 {
 199   mutex->counter = -1;
 200   mutex->depth = 0;
 201   mutex->owner = 0;
 202   mutex->sema = CreateSemaphore (NULL, 0, 65535, NULL);
 203 }
 204
 205 int
 206 __gthr_win32_recursive_mutex_lock (__gthread_recursive_mutex_t *mutex)
 207 {
 208   DWORD me = GetCurrentThreadId();
 209   if (InterlockedIncrement (&mutex->counter) == 0)
 210     {
 211       mutex->depth = 1;
 212       mutex->owner = me;
 213     }
 214   else if (mutex->owner == me)
 215     {
 216       InterlockedDecrement (&mutex->counter);
 217       ++(mutex->depth);
 218     }
 219   else if (WaitForSingleObject (mutex->sema, INFINITE) == WAIT_OBJECT_0)
 220     {
 221       mutex->depth = 1;
 222       mutex->owner = me;
 223     }
 224   else
 225     {
 226       /* WaitForSingleObject returns WAIT_FAILED, and we can only do
 227          some best-effort cleanup here.  */
 228       InterlockedDecrement (&mutex->counter);
 229       return 1;
 230     }
 231   return 0;
 232 }
 233
 234 int
 235 __gthr_win32_recursive_mutex_trylock (__gthread_recursive_mutex_t *mutex)
 236 {
 237   DWORD me = GetCurrentThreadId();
 238   if (__GTHR_W32_InterlockedCompareExchange (&mutex->counter, 0, -1) < 0)
 239     {
 240       mutex->depth = 1;
 241       mutex->owner = me;
 242     }
 243   else if (mutex->owner == me)
 244     ++(mutex->depth);
 245   else
 246     return 1;
 247
 248   return 0;
 249 }
 250
 251 int
 252 __gthr_win32_recursive_mutex_unlock (__gthread_recursive_mutex_t *mutex)
 253 {
 254   --(mutex->depth);
 255   if (mutex->depth == 0)
 256     {
 257       mutex->owner = 0;
 258
 259       if (InterlockedDecrement (&mutex->counter) >= 0)
 260         return ReleaseSemaphore (mutex->sema, 1, NULL) ? 0 : 1;
 261     }
 262
 263   return 0;
 264 }