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/*
* spin.c
*
* Description:
* This translation unit implements spin locks primitives.
*
* Pthreads-win32 - POSIX Threads Library for Win32
* Copyright (C) 1998
*
* This library 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 library 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.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the Free
* Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
* MA 02111-1307, USA
*/
#include "pthread.h"
#include "implement.h"
/*
* This works because the mask that is formed exposes all but the
* first two LSBs. If the spinlock is using a mutex rather than
* the interlock mechanism then there will always be high bits
* to indicate this. This is all just to save the overhead of
* using a non-simple struct for spinlocks.
*/
#define PTW32_SPIN_SPINS(_lock) \
(0 == ((long) ((_lock->u).mx) & ~(PTW32_SPIN_LOCKED | PTW32_SPIN_UNLOCKED | (long) PTW32_OBJECT_INVALID)))
int
pthread_spin_init(pthread_spinlock_t *lock, int pshared)
{
pthread_spinlock_t s;
int CPUs = 1;
int result = 0;
if (lock == NULL || *lock == NULL)
{
return EINVAL;
}
s = (pthread_spinlock_t) calloc(1, sizeof(*s));
if (s == NULL)
{
return ENOMEM;
}
(void) pthread_getprocessors_np(&CPUs);
if (CPUs > 1)
{
if (pshared == PTHREAD_PROCESS_SHARED)
{
/*
* Creating spinlock that can be shared between
* processes.
*/
#if _POSIX_THREAD_PROCESS_SHARED
/*
* Not implemented yet.
*/
#error ERROR [__FILE__, line __LINE__]: Process shared spin locks are not supported yet.
#else
result = ENOSYS;
goto FAIL0;
#endif /* _POSIX_THREAD_PROCESS_SHARED */
}
s->u.interlock = PTW32_SPIN_UNLOCKED;
}
else
{
pthread_mutexattr_t ma;
result = pthread_mutexattr_init(&ma);
if (0 == result)
{
ma->pshared = pshared;
result = pthread_mutex_init(&(s->u.mx), &ma);
}
}
FAIL0:
*lock = (0 == result ? s : NULL);
return(result);
}
int
pthread_spin_destroy(pthread_spinlock_t *lock)
{
pthread_spinlock_t s;
if (lock == NULL || *lock == NULL)
{
return EINVAL;
}
s = *lock;
if (PTW32_SPIN_SPINS(s))
{
if ( PTW32_SPIN_UNLOCKED !=
InterlockedCompareExchange((LPLONG) &(s->u.interlock),
(LONG) PTW32_OBJECT_INVALID,
(LONG) PTW32_SPIN_UNLOCKED))
{
return EINVAL;
}
else
{
return 0;
}
}
else
{
return pthread_mutex_destroy(&(s->u.mx));
}
}
int
pthread_spin_lock(pthread_spinlock_t *lock)
{
pthread_spinlock_t s;
if (lock == NULL || *lock == NULL)
{
return EINVAL;
}
s = *lock;
if (PTW32_SPIN_SPINS(s))
{
while ( PTW32_SPIN_UNLOCKED !=
InterlockedCompareExchange((LPLONG) &(s->u.interlock),
(LONG) PTW32_SPIN_LOCKED,
(LONG) PTW32_SPIN_UNLOCKED) )
{
/* Spin */
}
}
else
{
return pthread_mutex_lock(&(s->u.mx));
}
return 0;
}
int
pthread_spin_unlock(pthread_spinlock_t *lock)
{
pthread_spinlock_t s;
if (lock == NULL || lock == NULL)
{
return EINVAL;
}
s = *lock;
if (PTW32_SPIN_SPINS(s))
{
if (PTW32_SPIN_LOCKED !=
InterlockedCompareExchange((LPLONG) &(s->u.interlock),
(LONG) PTW32_SPIN_UNLOCKED,
(LONG) PTW32_SPIN_LOCKED ) )
{
return 0;
}
else
{
return EINVAL;
}
}
else
{
return pthread_mutex_unlock(&(s->u.mx));
}
}
int
pthread_spin_trylock(pthread_spinlock_t *lock)
{
pthread_spinlock_t s;
if (lock == NULL || *lock == NULL)
{
return EINVAL;
}
s = *lock;
if (PTW32_SPIN_SPINS(s))
{
if (PTW32_SPIN_UNLOCKED !=
InterlockedCompareExchange((LPLONG) &(s->u.interlock),
(LONG) PTW32_SPIN_LOCKED,
(LONG) PTW32_SPIN_UNLOCKED ) )
{
return EBUSY;
}
else
{
return 0;
}
}
else
{
return pthread_mutex_trylock(&(s->u.mx));
}
}
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