gcc/config/i386/gthr-win32.c

   1 /* Implementation of W32-specific threads compatibility routines for
   2    libgcc2.   */
   3
   4 /* Copyright (C) 1999, 2000, 2002 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, 59 Temple Place - Suite 330, Boston, MA
  24 02111-1307, 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 #ifndef __GTHREAD_HIDE_WIN32API
  35 # define __GTHREAD_HIDE_WIN32API 1
  36 #endif
  37 #include <gthr-win32.h>
  38 #include <windows.h>
  39
  40 /* Windows32 threads specific definitions. The windows32 threading model
  41    does not map well into pthread-inspired gcc's threading model, and so
  42    there are caveats one needs to be aware of.
  43
  44    1. The destructor supplied to __gthread_key_create is ignored for
  45       generic x86-win32 ports. This will certainly cause memory leaks
  46       due to unreclaimed eh contexts (sizeof (eh_context) is at least
  47       24 bytes for x86 currently).
  48
  49       This memory leak may be significant for long-running applications
  50       that make heavy use of C++ EH.
  51
  52       However, Mingw runtime (version 0.3 or newer) provides a mechanism
  53       to emulate pthreads key dtors; the runtime provides a special DLL,
  54       linked in if -mthreads option is specified, that runs the dtors in
  55       the reverse order of registration when each thread exits. If
  56       -mthreads option is not given, a stub is linked in instead of the
  57       DLL, which results in memory leak. Other x86-win32 ports can use
  58       the same technique of course to avoid the leak.
  59
  60    2. The error codes returned are non-POSIX like, and cast into ints.
  61       This may cause incorrect error return due to truncation values on
  62       hw where sizeof (DWORD) > sizeof (int).
  63
  64    3. We might consider using Critical Sections instead of Windows32
  65       mutexes for better performance, but emulating __gthread_mutex_trylock
  66       interface becomes more complicated (Win9x does not support
  67       TryEnterCriticalSectioni, while NT does).
  68
  69    The basic framework should work well enough. In the long term, GCC
  70    needs to use Structured Exception Handling on Windows32.  */
  71
  72 int
  73 __gthr_win32_once (__gthread_once_t *once, void (*func) (void))
  74 {
  75   if (once == NULL || func == NULL)
  76     return EINVAL;
  77
  78   if (! once->done)
  79     {
  80       if (InterlockedIncrement (&(once->started)) == 0)
  81         {
  82           (*func) ();
  83           once->done = TRUE;
  84         }
  85       else
  86         {
  87           /* Another thread is currently executing the code, so wait for it
  88              to finish; yield the CPU in the meantime.  If performance
  89              does become an issue, the solution is to use an Event that
  90              we wait on here (and set above), but that implies a place to
  91              create the event before this routine is called.  */
  92           while (! once->done)
  93             Sleep (0);
  94         }
  95     }
  96   return 0;
  97 }
  98
  99 /* Windows32 thread local keys don't support destructors; this leads to
 100    leaks, especially in threaded applications making extensive use of
 101    C++ EH. Mingw uses a thread-support DLL to work-around this problem.  */
 102
 103 int
 104 __gthr_win32_key_create (__gthread_key_t *key, void (*dtor) (void *))
 105 {
 106   int status = 0;
 107   DWORD tls_index = TlsAlloc ();
 108   if (tls_index != 0xFFFFFFFF)
 109     {
 110       *key = tls_index;
 111 #ifdef MINGW32_SUPPORTS_MT_EH
 112       /* Mingw runtime will run the dtors in reverse order for each thread
 113          when the thread exits.  */
 114       status = __mingwthr_key_dtor (*key, dtor);
 115 #endif
 116     }
 117   else
 118     status = (int) GetLastError ();
 119   return status;
 120 }
 121
 122 int
 123 __gthr_win32_key_delete (__gthread_key_t key)
 124 {
 125   return (TlsFree (key) != 0) ? 0 : (int) GetLastError ();
 126 }
 127
 128 void *
 129 __gthr_win32_getspecific (__gthread_key_t key)
 130 {
 131   DWORD lasterror;
 132   void *ptr;
 133   lasterror = GetLastError();
 134   ptr = TlsGetValue(key);
 135   SetLastError( lasterror );
 136   return ptr;
 137 }
 138
 139 int
 140 __gthr_win32_setspecific (__gthread_key_t key, const void *ptr)
 141 {
 142   return (TlsSetValue (key, (void*) ptr) != 0) ? 0 : (int) GetLastError ();
 143 }
 144
 145 void
 146 __gthr_win32_mutex_init_function (__gthread_mutex_t *mutex)
 147 {
 148   /* Create unnamed mutex with default security attr and no initial owner.  */
 149   *mutex = CreateMutex (NULL, 0, NULL);
 150 }
 151
 152 int
 153 __gthr_win32_mutex_lock (__gthread_mutex_t *mutex)
 154 {
 155   if (WaitForSingleObject (*mutex, INFINITE) == WAIT_OBJECT_0)
 156     return 0;
 157   else
 158     return 1;
 159 }
 160
 161 int
 162 __gthr_win32_mutex_trylock (__gthread_mutex_t *mutex)
 163 {
 164   if (WaitForSingleObject (*mutex, 0) == WAIT_OBJECT_0)
 165     return 0;
 166   else
 167     return 1;
 168 }
 169
 170 int
 171 __gthr_win32_mutex_unlock (__gthread_mutex_t *mutex)
 172 {
 173     return (ReleaseMutex (*mutex) != 0) ? 0 : 1;
 174 }