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