1/* Implementation of W32-specific threads compatibility routines for
2   libgcc2.  */
3
4/* Copyright (C) 1999, 2000, 2002, 2004 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 2, 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
21You should have received a copy of the GNU General Public License
22along with GCC; see the file COPYING.  If not, write to the Free
23Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
2402110-1301, 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
73int
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
104int
105__gthr_win32_key_create (__gthread_key_t *key, void (*dtor) (void *))
106{
107  int status = 0;
108  DWORD tls_index = TlsAlloc ();
109  if (tls_index != 0xFFFFFFFF)
110    {
111      *key = tls_index;
112#ifdef MINGW32_SUPPORTS_MT_EH
113      /* Mingw runtime will run the dtors in reverse order for each thread
114         when the thread exits.  */
115      status = __mingwthr_key_dtor (*key, dtor);
116#endif
117    }
118  else
119    status = (int) GetLastError ();
120  return status;
121}
122
123int
124__gthr_win32_key_delete (__gthread_key_t key)
125{
126  return (TlsFree (key) != 0) ? 0 : (int) GetLastError ();
127}
128
129void *
130__gthr_win32_getspecific (__gthread_key_t key)
131{
132  DWORD lasterror;
133  void *ptr;
134  lasterror = GetLastError();
135  ptr = TlsGetValue(key);
136  SetLastError( lasterror );
137  return ptr;
138}
139
140int
141__gthr_win32_setspecific (__gthread_key_t key, const void *ptr)
142{
143  return (TlsSetValue (key, (void*) ptr) != 0) ? 0 : (int) GetLastError ();
144}
145
146void
147__gthr_win32_mutex_init_function (__gthread_mutex_t *mutex)
148{
149  mutex->counter = -1;
150  mutex->sema = CreateSemaphore (NULL, 0, 65535, NULL);
151}
152
153int
154__gthr_win32_mutex_lock (__gthread_mutex_t *mutex)
155{
156  if (InterlockedIncrement (&mutex->counter) == 0 ||
157      WaitForSingleObject (mutex->sema, INFINITE) == WAIT_OBJECT_0)
158    return 0;
159  else
160    {
161      /* WaitForSingleObject returns WAIT_FAILED, and we can only do
162         some best-effort cleanup here.  */
163      InterlockedDecrement (&mutex->counter);
164      return 1;
165    }
166}
167
168int
169__gthr_win32_mutex_trylock (__gthread_mutex_t *mutex)
170{
171  if (__GTHR_W32_InterlockedCompareExchange (&mutex->counter, 0, -1) < 0)
172    return 0;
173  else
174    return 1;
175}
176
177int
178__gthr_win32_mutex_unlock (__gthread_mutex_t *mutex)
179{
180  if (InterlockedDecrement (&mutex->counter) >= 0)
181    return ReleaseSemaphore (mutex->sema, 1, NULL) ? 0 : 1;
182  else
183    return 0;
184}
185
186void
187__gthr_win32_recursive_mutex_init_function (__gthread_recursive_mutex_t *mutex)
188{
189  mutex->counter = -1;
190  mutex->depth = 0;
191  mutex->owner = 0;
192  mutex->sema = CreateSemaphore (NULL, 0, 65535, NULL);
193}
194
195int
196__gthr_win32_recursive_mutex_lock (__gthread_recursive_mutex_t *mutex)
197{
198  DWORD me = GetCurrentThreadId();
199  if (InterlockedIncrement (&mutex->counter) == 0)
200    {
201      mutex->depth = 1;
202      mutex->owner = me;
203    }
204  else if (mutex->owner == me)
205    {
206      InterlockedDecrement (&mutex->counter);
207      ++(mutex->depth);
208    }
209  else if (WaitForSingleObject (mutex->sema, INFINITE) == WAIT_OBJECT_0)
210    {
211      mutex->depth = 1;
212      mutex->owner = me;
213    }
214  else
215    {
216      /* WaitForSingleObject returns WAIT_FAILED, and we can only do
217         some best-effort cleanup here.  */
218      InterlockedDecrement (&mutex->counter);
219      return 1;
220    }
221  return 0;
222}
223
224int
225__gthr_win32_recursive_mutex_trylock (__gthread_recursive_mutex_t *mutex)
226{
227  DWORD me = GetCurrentThreadId();
228  if (__GTHR_W32_InterlockedCompareExchange (&mutex->counter, 0, -1) < 0)
229    {
230      mutex->depth = 1;
231      mutex->owner = me;
232    }
233  else if (mutex->owner == me)
234    ++(mutex->depth);
235  else
236    return 1;
237
238  return 0;
239}
240
241int
242__gthr_win32_recursive_mutex_unlock (__gthread_recursive_mutex_t *mutex)
243{
244  --(mutex->depth);
245  if (mutex->depth == 0)
246    {
247      mutex->owner = 0;
248
249      if (InterlockedDecrement (&mutex->counter) >= 0)
250	return ReleaseSemaphore (mutex->sema, 1, NULL) ? 0 : 1;
251    }
252
253  return 0;
254}
255