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[/] [openrisc/] [trunk/] [gnu-stable/] [newlib-1.18.0/] [newlib/] [libc/] [sys/] [linux/] [linuxthreads/] [mutex.c] - Blame information for rev 207

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/* Linuxthreads - a simple clone()-based implementation of Posix        */
/* threads for Linux.                                                   */
/* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr)              */
/*                                                                      */
/* This program is free software; you can redistribute it and/or        */
/* modify it under the terms of the GNU Library General Public License  */
/* as published by the Free Software Foundation; either version 2       */
/* of the License, or (at your option) any later version.               */
/*                                                                      */
/* This program is distributed in the hope that it will be useful,      */
/* but WITHOUT ANY WARRANTY; without even the implied warranty of       */
/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the        */
/* GNU Library General Public License for more details.                 */
 
/* Mutexes */
 
#include <bits/libc-lock.h>
#include <errno.h>
#include <sched.h>
#include <stddef.h>
#include <limits.h>
#include "pthread.h"
#include "internals.h"
#include "spinlock.h"
#include "queue.h"
#include "restart.h"
 
int __pthread_mutex_init(pthread_mutex_t * mutex,
                       const pthread_mutexattr_t * mutex_attr)
{
  __pthread_init_lock(&mutex->__m_lock);
  mutex->__m_kind =
    mutex_attr == NULL ? PTHREAD_MUTEX_TIMED_NP : mutex_attr->__mutexkind;
  mutex->__m_count = 0;
  mutex->__m_owner = NULL;
  return 0;
}
strong_alias (__pthread_mutex_init, pthread_mutex_init)
 
int __pthread_mutex_destroy(pthread_mutex_t * mutex)
{
  switch (mutex->__m_kind) {
  case PTHREAD_MUTEX_ADAPTIVE_NP:
  case PTHREAD_MUTEX_RECURSIVE_NP:
    if ((mutex->__m_lock.__status & 1) != 0)
      return EBUSY;
    return 0;
  case PTHREAD_MUTEX_ERRORCHECK_NP:
  case PTHREAD_MUTEX_TIMED_NP:
    if (mutex->__m_lock.__status != 0)
      return EBUSY;
    return 0;
  default:
    return EINVAL;
  }
}
strong_alias (__pthread_mutex_destroy, pthread_mutex_destroy)
 
int __pthread_mutex_trylock(pthread_mutex_t * mutex)
{
  pthread_descr self;
  int retcode;
 
  switch(mutex->__m_kind) {
  case PTHREAD_MUTEX_ADAPTIVE_NP:
    retcode = __pthread_trylock(&mutex->__m_lock);
    return retcode;
  case PTHREAD_MUTEX_RECURSIVE_NP:
    self = thread_self();
    if (mutex->__m_owner == self) {
      mutex->__m_count++;
      return 0;
    }
    retcode = __pthread_trylock(&mutex->__m_lock);
    if (retcode == 0) {
      mutex->__m_owner = self;
      mutex->__m_count = 0;
    }
    return retcode;
  case PTHREAD_MUTEX_ERRORCHECK_NP:
    retcode = __pthread_alt_trylock(&mutex->__m_lock);
    if (retcode == 0) {
      mutex->__m_owner = thread_self();
    }
    return retcode;
  case PTHREAD_MUTEX_TIMED_NP:
    retcode = __pthread_alt_trylock(&mutex->__m_lock);
    return retcode;
  default:
    return EINVAL;
  }
}
strong_alias (__pthread_mutex_trylock, pthread_mutex_trylock)
 
int __pthread_mutex_lock(pthread_mutex_t * mutex)
{
  pthread_descr self;
 
  switch(mutex->__m_kind) {
  case PTHREAD_MUTEX_ADAPTIVE_NP:
    __pthread_lock(&mutex->__m_lock, NULL);
    return 0;
  case PTHREAD_MUTEX_RECURSIVE_NP:
    self = thread_self();
    if (mutex->__m_owner == self) {
      mutex->__m_count++;
      return 0;
    }
    __pthread_lock(&mutex->__m_lock, self);
    mutex->__m_owner = self;
    mutex->__m_count = 0;
    return 0;
  case PTHREAD_MUTEX_ERRORCHECK_NP:
    self = thread_self();
    if (mutex->__m_owner == self) return EDEADLK;
    __pthread_alt_lock(&mutex->__m_lock, self);
    mutex->__m_owner = self;
    return 0;
  case PTHREAD_MUTEX_TIMED_NP:
    __pthread_alt_lock(&mutex->__m_lock, NULL);
    return 0;
  default:
    return EINVAL;
  }
}
strong_alias (__pthread_mutex_lock, pthread_mutex_lock)
 
int __pthread_mutex_timedlock (pthread_mutex_t *mutex,
                               const struct timespec *abstime)
{
  pthread_descr self;
  int res;
 
  if (__builtin_expect (abstime->tv_nsec, 0) < 0
      || __builtin_expect (abstime->tv_nsec, 0) >= 1000000000)
    return EINVAL;
 
  switch(mutex->__m_kind) {
  case PTHREAD_MUTEX_ADAPTIVE_NP:
    __pthread_lock(&mutex->__m_lock, NULL);
    return 0;
  case PTHREAD_MUTEX_RECURSIVE_NP:
    self = thread_self();
    if (mutex->__m_owner == self) {
      mutex->__m_count++;
      return 0;
    }
    __pthread_lock(&mutex->__m_lock, self);
    mutex->__m_owner = self;
    mutex->__m_count = 0;
    return 0;
  case PTHREAD_MUTEX_ERRORCHECK_NP:
    self = thread_self();
    if (mutex->__m_owner == self) return EDEADLK;
    res = __pthread_alt_timedlock(&mutex->__m_lock, self, abstime);
    if (res != 0)
      {
        mutex->__m_owner = self;
        return 0;
      }
    return ETIMEDOUT;
  case PTHREAD_MUTEX_TIMED_NP:
    /* Only this type supports timed out lock. */
    return (__pthread_alt_timedlock(&mutex->__m_lock, NULL, abstime)
            ? 0 : ETIMEDOUT);
  default:
    return EINVAL;
  }
}
strong_alias (__pthread_mutex_timedlock, pthread_mutex_timedlock)
 
int __pthread_mutex_unlock(pthread_mutex_t * mutex)
{
  switch (mutex->__m_kind) {
  case PTHREAD_MUTEX_ADAPTIVE_NP:
    __pthread_unlock(&mutex->__m_lock);
    return 0;
  case PTHREAD_MUTEX_RECURSIVE_NP:
    if (mutex->__m_owner != thread_self())
      return EPERM;
    if (mutex->__m_count > 0) {
      mutex->__m_count--;
      return 0;
    }
    mutex->__m_owner = NULL;
    __pthread_unlock(&mutex->__m_lock);
    return 0;
  case PTHREAD_MUTEX_ERRORCHECK_NP:
    if (mutex->__m_owner != thread_self() || mutex->__m_lock.__status == 0)
      return EPERM;
    mutex->__m_owner = NULL;
    __pthread_alt_unlock(&mutex->__m_lock);
    return 0;
  case PTHREAD_MUTEX_TIMED_NP:
    __pthread_alt_unlock(&mutex->__m_lock);
    return 0;
  default:
    return EINVAL;
  }
}
strong_alias (__pthread_mutex_unlock, pthread_mutex_unlock)
 
int __pthread_mutexattr_init(pthread_mutexattr_t *attr)
{
  attr->__mutexkind = PTHREAD_MUTEX_TIMED_NP;
  return 0;
}
strong_alias (__pthread_mutexattr_init, pthread_mutexattr_init)
 
int __pthread_mutexattr_destroy(pthread_mutexattr_t *attr)
{
  return 0;
}
strong_alias (__pthread_mutexattr_destroy, pthread_mutexattr_destroy)
 
int __pthread_mutexattr_settype(pthread_mutexattr_t *attr, int kind)
{
  if (kind != PTHREAD_MUTEX_ADAPTIVE_NP
      && kind != PTHREAD_MUTEX_RECURSIVE_NP
      && kind != PTHREAD_MUTEX_ERRORCHECK_NP
      && kind != PTHREAD_MUTEX_TIMED_NP)
    return EINVAL;
  attr->__mutexkind = kind;
  return 0;
}
weak_alias (__pthread_mutexattr_settype, pthread_mutexattr_settype)
#if !defined(_ELIX_LEVEL) || _ELIX_LEVEL >= 2
strong_alias ( __pthread_mutexattr_settype, __pthread_mutexattr_setkind_np)
weak_alias (__pthread_mutexattr_setkind_np, pthread_mutexattr_setkind_np)
#endif /* !_ELIX_LEVEL || _ELIX_LEVEL >= 2 */
 
int __pthread_mutexattr_gettype(const pthread_mutexattr_t *attr, int *kind)
{
  *kind = attr->__mutexkind;
  return 0;
}
weak_alias (__pthread_mutexattr_gettype, pthread_mutexattr_gettype)
#if !defined(_ELIX_LEVEL) || _ELIX_LEVEL >= 2
strong_alias (__pthread_mutexattr_gettype, __pthread_mutexattr_getkind_np)
weak_alias (__pthread_mutexattr_getkind_np, pthread_mutexattr_getkind_np)
#endif /* !_ELIX_LEVEL || _ELIX_LEVEL >= 2 */
 
 
#if !defined(_ELIX_LEVEL) || _ELIX_LEVEL >= 3
 
int __pthread_mutexattr_getpshared (const pthread_mutexattr_t *attr,
                                   int *pshared)
{
  *pshared = PTHREAD_PROCESS_PRIVATE;
  return 0;
}
weak_alias (__pthread_mutexattr_getpshared, pthread_mutexattr_getpshared)
 
int __pthread_mutexattr_setpshared (pthread_mutexattr_t *attr, int pshared)
{
  if (pshared != PTHREAD_PROCESS_PRIVATE && pshared != PTHREAD_PROCESS_SHARED)
    return EINVAL;
 
  /* For now it is not possible to shared a conditional variable.  */
  if (pshared != PTHREAD_PROCESS_PRIVATE)
    return ENOSYS;
 
  return 0;
}
weak_alias (__pthread_mutexattr_setpshared, pthread_mutexattr_setpshared)
 
#endif /* !_ELIX_LEVEL || _ELIX_LEVEL >= 3 */
 
/* Once-only execution */
 
static pthread_mutex_t once_masterlock = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t once_finished = PTHREAD_COND_INITIALIZER;
static int fork_generation = 0;  /* Child process increments this after fork. */
 
enum { NEVER = 0, IN_PROGRESS = 1, DONE = 2 };
 
/* If a thread is canceled while calling the init_routine out of
   pthread once, this handler will reset the once_control variable
   to the NEVER state. */
 
static void pthread_once_cancelhandler(void *arg)
{
    pthread_once_t *once_control = arg;
 
    pthread_mutex_lock(&once_masterlock);
    *once_control = NEVER;
    pthread_mutex_unlock(&once_masterlock);
    pthread_cond_broadcast(&once_finished);
}
 
int __pthread_once(pthread_once_t * once_control, void (*init_routine)(void))
{
  /* flag for doing the condition broadcast outside of mutex */
  int state_changed;
 
  /* Test without locking first for speed */
  if (*once_control == DONE) {
    READ_MEMORY_BARRIER();
    return 0;
  }
  /* Lock and test again */
 
  state_changed = 0;
 
  pthread_mutex_lock(&once_masterlock);
 
  /* If this object was left in an IN_PROGRESS state in a parent
     process (indicated by stale generation field), reset it to NEVER. */
  if ((*once_control & 3) == IN_PROGRESS && (*once_control & ~3) != fork_generation)
    *once_control = NEVER;
 
  /* If init_routine is being called from another routine, wait until
     it completes. */
  while ((*once_control & 3) == IN_PROGRESS) {
    pthread_cond_wait(&once_finished, &once_masterlock);
  }
  /* Here *once_control is stable and either NEVER or DONE. */
  if (*once_control == NEVER) {
    *once_control = IN_PROGRESS | fork_generation;
    pthread_mutex_unlock(&once_masterlock);
    pthread_cleanup_push(pthread_once_cancelhandler, once_control);
    init_routine();
    pthread_cleanup_pop(0);
    pthread_mutex_lock(&once_masterlock);
    WRITE_MEMORY_BARRIER();
    *once_control = DONE;
    state_changed = 1;
  }
  pthread_mutex_unlock(&once_masterlock);
 
  if (state_changed)
    pthread_cond_broadcast(&once_finished);
 
  return 0;
}
strong_alias (__pthread_once, pthread_once)
 
/*
 * Handle the state of the pthread_once mechanism across forks.  The
 * once_masterlock is acquired in the parent process prior to a fork to ensure
 * that no thread is in the critical region protected by the lock.  After the
 * fork, the lock is released. In the child, the lock and the condition
 * variable are simply reset.  The child also increments its generation
 * counter which lets pthread_once calls detect stale IN_PROGRESS states
 * and reset them back to NEVER.
 */
 
void __pthread_once_fork_prepare(void)
{
  pthread_mutex_lock(&once_masterlock);
}
 
void __pthread_once_fork_parent(void)
{
  pthread_mutex_unlock(&once_masterlock);
}
 
void __pthread_once_fork_child(void)
{
  pthread_mutex_init(&once_masterlock, NULL);
  pthread_cond_init(&once_finished, NULL);
  if (fork_generation <= INT_MAX - 4)
    fork_generation += 4;       /* leave least significant two bits zero */
  else
    fork_generation = 0;
}

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[/] [openrisc/] [trunk/] [gnu-stable/] [newlib-1.18.0/] [newlib/] [libc/] [sys/] [linux/] [linuxthreads/] [mutex.c] - Blame information for rev 207

Line No.	Rev	Author	Line
1	207	jeremybenn	`/* Linuxthreads - a simple clone()-based implementation of Posix */`
2			`/* threads for Linux. */`
3			`/* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr) */`
4			`/* */`
5			`/* This program is free software; you can redistribute it and/or */`
6			`/* modify it under the terms of the GNU Library General Public License */`
7			`/* as published by the Free Software Foundation; either version 2 */`
8			`/* of the License, or (at your option) any later version. */`
9			`/* */`
10			`/* This program is distributed in the hope that it will be useful, */`
11			`/* but WITHOUT ANY WARRANTY; without even the implied warranty of */`
12			`/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the */`
13			`/* GNU Library General Public License for more details. */`
14
15			`/* Mutexes */`
16
17			`#include <bits/libc-lock.h>`
18			`#include <errno.h>`
19			`#include <sched.h>`
20			`#include <stddef.h>`
21			`#include <limits.h>`
22			`#include "pthread.h"`
23			`#include "internals.h"`
24			`#include "spinlock.h"`
25			`#include "queue.h"`
26			`#include "restart.h"`
27
28			`int __pthread_mutex_init(pthread_mutex_t * mutex,`
29			`const pthread_mutexattr_t * mutex_attr)`
30			`{`
31			`__pthread_init_lock(&mutex->__m_lock);`
32			`mutex->__m_kind =`
33			`mutex_attr == NULL ? PTHREAD_MUTEX_TIMED_NP : mutex_attr->__mutexkind;`
34			`mutex->__m_count = 0;`
35			`mutex->__m_owner = NULL;`
36			`return 0;`
37			`}`
38			`strong_alias (__pthread_mutex_init, pthread_mutex_init)`
39
40			`int __pthread_mutex_destroy(pthread_mutex_t * mutex)`
41			`{`
42			`switch (mutex->__m_kind) {`
43			`case PTHREAD_MUTEX_ADAPTIVE_NP:`
44			`case PTHREAD_MUTEX_RECURSIVE_NP:`
45			`if ((mutex->__m_lock.__status & 1) != 0)`
46			`return EBUSY;`
47			`return 0;`
48			`case PTHREAD_MUTEX_ERRORCHECK_NP:`
49			`case PTHREAD_MUTEX_TIMED_NP:`
50			`if (mutex->__m_lock.__status != 0)`
51			`return EBUSY;`
52			`return 0;`
53			`default:`
54			`return EINVAL;`
55			`}`
56			`}`
57			`strong_alias (__pthread_mutex_destroy, pthread_mutex_destroy)`
58
59			`int __pthread_mutex_trylock(pthread_mutex_t * mutex)`
60			`{`
61			`pthread_descr self;`
62			`int retcode;`
63
64			`switch(mutex->__m_kind) {`
65			`case PTHREAD_MUTEX_ADAPTIVE_NP:`
66			`retcode = __pthread_trylock(&mutex->__m_lock);`
67			`return retcode;`
68			`case PTHREAD_MUTEX_RECURSIVE_NP:`
69			`self = thread_self();`
70			`if (mutex->__m_owner == self) {`
71			`mutex->__m_count++;`
72			`return 0;`
73			`}`
74			`retcode = __pthread_trylock(&mutex->__m_lock);`
75			`if (retcode == 0) {`
76			`mutex->__m_owner = self;`
77			`mutex->__m_count = 0;`
78			`}`
79			`return retcode;`
80			`case PTHREAD_MUTEX_ERRORCHECK_NP:`
81			`retcode = __pthread_alt_trylock(&mutex->__m_lock);`
82			`if (retcode == 0) {`
83			`mutex->__m_owner = thread_self();`
84			`}`
85			`return retcode;`
86			`case PTHREAD_MUTEX_TIMED_NP:`
87			`retcode = __pthread_alt_trylock(&mutex->__m_lock);`
88			`return retcode;`
89			`default:`
90			`return EINVAL;`
91			`}`
92			`}`
93			`strong_alias (__pthread_mutex_trylock, pthread_mutex_trylock)`
94
95			`int __pthread_mutex_lock(pthread_mutex_t * mutex)`
96			`{`
97			`pthread_descr self;`
98
99			`switch(mutex->__m_kind) {`
100			`case PTHREAD_MUTEX_ADAPTIVE_NP:`
101			`__pthread_lock(&mutex->__m_lock, NULL);`
102			`return 0;`
103			`case PTHREAD_MUTEX_RECURSIVE_NP:`
104			`self = thread_self();`
105			`if (mutex->__m_owner == self) {`
106			`mutex->__m_count++;`
107			`return 0;`
108			`}`
109			`__pthread_lock(&mutex->__m_lock, self);`
110			`mutex->__m_owner = self;`
111			`mutex->__m_count = 0;`
112			`return 0;`
113			`case PTHREAD_MUTEX_ERRORCHECK_NP:`
114			`self = thread_self();`
115			`if (mutex->__m_owner == self) return EDEADLK;`
116			`__pthread_alt_lock(&mutex->__m_lock, self);`
117			`mutex->__m_owner = self;`
118			`return 0;`
119			`case PTHREAD_MUTEX_TIMED_NP:`
120			`__pthread_alt_lock(&mutex->__m_lock, NULL);`
121			`return 0;`
122			`default:`
123			`return EINVAL;`
124			`}`
125			`}`
126			`strong_alias (__pthread_mutex_lock, pthread_mutex_lock)`
127
128			`int __pthread_mutex_timedlock (pthread_mutex_t *mutex,`
129			`const struct timespec *abstime)`
130			`{`
131			`pthread_descr self;`
132			`int res;`
133
134			`if (__builtin_expect (abstime->tv_nsec, 0) < 0`
135			`\|\| __builtin_expect (abstime->tv_nsec, 0) >= 1000000000)`
136			`return EINVAL;`
137
138			`switch(mutex->__m_kind) {`
139			`case PTHREAD_MUTEX_ADAPTIVE_NP:`
140			`__pthread_lock(&mutex->__m_lock, NULL);`
141			`return 0;`
142			`case PTHREAD_MUTEX_RECURSIVE_NP:`
143			`self = thread_self();`
144			`if (mutex->__m_owner == self) {`
145			`mutex->__m_count++;`
146			`return 0;`
147			`}`
148			`__pthread_lock(&mutex->__m_lock, self);`
149			`mutex->__m_owner = self;`
150			`mutex->__m_count = 0;`
151			`return 0;`
152			`case PTHREAD_MUTEX_ERRORCHECK_NP:`
153			`self = thread_self();`
154			`if (mutex->__m_owner == self) return EDEADLK;`
155			`res = __pthread_alt_timedlock(&mutex->__m_lock, self, abstime);`
156			`if (res != 0)`
157			`{`
158			`mutex->__m_owner = self;`
159			`return 0;`
160			`}`
161			`return ETIMEDOUT;`
162			`case PTHREAD_MUTEX_TIMED_NP:`
163			`/* Only this type supports timed out lock. */`
164			`return (__pthread_alt_timedlock(&mutex->__m_lock, NULL, abstime)`
165			`? 0 : ETIMEDOUT);`
166			`default:`
167			`return EINVAL;`
168			`}`
169			`}`
170			`strong_alias (__pthread_mutex_timedlock, pthread_mutex_timedlock)`
171
172			`int __pthread_mutex_unlock(pthread_mutex_t * mutex)`
173			`{`
174			`switch (mutex->__m_kind) {`
175			`case PTHREAD_MUTEX_ADAPTIVE_NP:`
176			`__pthread_unlock(&mutex->__m_lock);`
177			`return 0;`
178			`case PTHREAD_MUTEX_RECURSIVE_NP:`
179			`if (mutex->__m_owner != thread_self())`
180			`return EPERM;`
181			`if (mutex->__m_count > 0) {`
182			`mutex->__m_count--;`
183			`return 0;`
184			`}`
185			`mutex->__m_owner = NULL;`
186			`__pthread_unlock(&mutex->__m_lock);`
187			`return 0;`
188			`case PTHREAD_MUTEX_ERRORCHECK_NP:`
189			`if (mutex->__m_owner != thread_self() \|\| mutex->__m_lock.__status == 0)`
190			`return EPERM;`
191			`mutex->__m_owner = NULL;`
192			`__pthread_alt_unlock(&mutex->__m_lock);`
193			`return 0;`
194			`case PTHREAD_MUTEX_TIMED_NP:`
195			`__pthread_alt_unlock(&mutex->__m_lock);`
196			`return 0;`
197			`default:`
198			`return EINVAL;`
199			`}`
200			`}`
201			`strong_alias (__pthread_mutex_unlock, pthread_mutex_unlock)`
202
203			`int __pthread_mutexattr_init(pthread_mutexattr_t *attr)`
204			`{`
205			`attr->__mutexkind = PTHREAD_MUTEX_TIMED_NP;`
206			`return 0;`
207			`}`
208			`strong_alias (__pthread_mutexattr_init, pthread_mutexattr_init)`
209
210			`int __pthread_mutexattr_destroy(pthread_mutexattr_t *attr)`
211			`{`
212			`return 0;`
213			`}`
214			`strong_alias (__pthread_mutexattr_destroy, pthread_mutexattr_destroy)`
215
216			`int __pthread_mutexattr_settype(pthread_mutexattr_t *attr, int kind)`
217			`{`
218			`if (kind != PTHREAD_MUTEX_ADAPTIVE_NP`
219			`&& kind != PTHREAD_MUTEX_RECURSIVE_NP`
220			`&& kind != PTHREAD_MUTEX_ERRORCHECK_NP`
221			`&& kind != PTHREAD_MUTEX_TIMED_NP)`
222			`return EINVAL;`
223			`attr->__mutexkind = kind;`
224			`return 0;`
225			`}`
226			`weak_alias (__pthread_mutexattr_settype, pthread_mutexattr_settype)`
227			`#if !defined(_ELIX_LEVEL) \|\| _ELIX_LEVEL >= 2`
228			`strong_alias ( __pthread_mutexattr_settype, __pthread_mutexattr_setkind_np)`
229			`weak_alias (__pthread_mutexattr_setkind_np, pthread_mutexattr_setkind_np)`
230			`#endif /* !_ELIX_LEVEL \|\| _ELIX_LEVEL >= 2 */`
231
232			`int __pthread_mutexattr_gettype(const pthread_mutexattr_t attr, int kind)`
233			`{`
234			`*kind = attr->__mutexkind;`
235			`return 0;`
236			`}`
237			`weak_alias (__pthread_mutexattr_gettype, pthread_mutexattr_gettype)`
238			`#if !defined(_ELIX_LEVEL) \|\| _ELIX_LEVEL >= 2`
239			`strong_alias (__pthread_mutexattr_gettype, __pthread_mutexattr_getkind_np)`
240			`weak_alias (__pthread_mutexattr_getkind_np, pthread_mutexattr_getkind_np)`
241			`#endif /* !_ELIX_LEVEL \|\| _ELIX_LEVEL >= 2 */`
242
243
244			`#if !defined(_ELIX_LEVEL) \|\| _ELIX_LEVEL >= 3`
245
246			`int __pthread_mutexattr_getpshared (const pthread_mutexattr_t *attr,`
247			`int *pshared)`
248			`{`
249			`*pshared = PTHREAD_PROCESS_PRIVATE;`
250			`return 0;`
251			`}`
252			`weak_alias (__pthread_mutexattr_getpshared, pthread_mutexattr_getpshared)`
253
254			`int __pthread_mutexattr_setpshared (pthread_mutexattr_t *attr, int pshared)`
255			`{`
256			`if (pshared != PTHREAD_PROCESS_PRIVATE && pshared != PTHREAD_PROCESS_SHARED)`
257			`return EINVAL;`
258
259			`/* For now it is not possible to shared a conditional variable. */`
260			`if (pshared != PTHREAD_PROCESS_PRIVATE)`
261			`return ENOSYS;`
262
263			`return 0;`
264			`}`
265			`weak_alias (__pthread_mutexattr_setpshared, pthread_mutexattr_setpshared)`
266
267			`#endif /* !_ELIX_LEVEL \|\| _ELIX_LEVEL >= 3 */`
268
269			`/* Once-only execution */`
270
271			`static pthread_mutex_t once_masterlock = PTHREAD_MUTEX_INITIALIZER;`
272			`static pthread_cond_t once_finished = PTHREAD_COND_INITIALIZER;`
273			`static int fork_generation = 0; /* Child process increments this after fork. */`
274
275			`enum { NEVER = 0, IN_PROGRESS = 1, DONE = 2 };`
276
277			`/* If a thread is canceled while calling the init_routine out of`
278			`pthread once, this handler will reset the once_control variable`
279			`to the NEVER state. */`
280
281			`static void pthread_once_cancelhandler(void *arg)`
282			`{`
283			`pthread_once_t *once_control = arg;`
284
285			`pthread_mutex_lock(&once_masterlock);`
286			`*once_control = NEVER;`
287			`pthread_mutex_unlock(&once_masterlock);`
288			`pthread_cond_broadcast(&once_finished);`
289			`}`
290
291			`int __pthread_once(pthread_once_t * once_control, void (*init_routine)(void))`
292			`{`
293			`/* flag for doing the condition broadcast outside of mutex */`
294			`int state_changed;`
295
296			`/* Test without locking first for speed */`
297			`if (*once_control == DONE) {`
298			`READ_MEMORY_BARRIER();`
299			`return 0;`
300			`}`
301			`/* Lock and test again */`
302
303			`state_changed = 0;`
304
305			`pthread_mutex_lock(&once_masterlock);`
306
307			`/* If this object was left in an IN_PROGRESS state in a parent`
308			`process (indicated by stale generation field), reset it to NEVER. */`
309			`if ((once_control & 3) == IN_PROGRESS && (once_control & ~3) != fork_generation)`
310			`*once_control = NEVER;`
311
312			`/* If init_routine is being called from another routine, wait until`
313			`it completes. */`
314			`while ((*once_control & 3) == IN_PROGRESS) {`
315			`pthread_cond_wait(&once_finished, &once_masterlock);`
316			`}`
317			`/* Here once_control is stable and either NEVER or DONE. /`
318			`if (*once_control == NEVER) {`
319			`*once_control = IN_PROGRESS \| fork_generation;`
320			`pthread_mutex_unlock(&once_masterlock);`
321			`pthread_cleanup_push(pthread_once_cancelhandler, once_control);`
322			`init_routine();`
323			`pthread_cleanup_pop(0);`
324			`pthread_mutex_lock(&once_masterlock);`
325			`WRITE_MEMORY_BARRIER();`
326			`*once_control = DONE;`
327			`state_changed = 1;`
328			`}`
329			`pthread_mutex_unlock(&once_masterlock);`
330
331			`if (state_changed)`
332			`pthread_cond_broadcast(&once_finished);`
333
334			`return 0;`
335			`}`
336			`strong_alias (__pthread_once, pthread_once)`
337
338			`/*`
339			`* Handle the state of the pthread_once mechanism across forks. The`
340			`* once_masterlock is acquired in the parent process prior to a fork to ensure`
341			`* that no thread is in the critical region protected by the lock. After the`
342			`* fork, the lock is released. In the child, the lock and the condition`
343			`* variable are simply reset. The child also increments its generation`
344			`* counter which lets pthread_once calls detect stale IN_PROGRESS states`
345			`* and reset them back to NEVER.`
346			`*/`
347
348			`void __pthread_once_fork_prepare(void)`
349			`{`
350			`pthread_mutex_lock(&once_masterlock);`
351			`}`
352
353			`void __pthread_once_fork_parent(void)`
354			`{`
355			`pthread_mutex_unlock(&once_masterlock);`
356			`}`
357
358			`void __pthread_once_fork_child(void)`
359			`{`
360			`pthread_mutex_init(&once_masterlock, NULL);`
361			`pthread_cond_init(&once_finished, NULL);`
362			`if (fork_generation <= INT_MAX - 4)`
363			`fork_generation += 4; /* leave least significant two bits zero */`
364			`else`
365			`fork_generation = 0;`
366			`}`