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/* POSIX spin locks.
Copyright (C) 2010-2020 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, see <https://www.gnu.org/licenses/>. */
/* Written by Paul Eggert, 2010, and Bruno Haible <bruno@clisp.org>, 2019. */
#include <config.h>
/* Specification. */
#include <pthread.h>
#if (defined _WIN32 && ! defined __CYGWIN__) && USE_WINDOWS_THREADS
# include "windows-spin.h"
#endif
#if (defined _WIN32 && ! defined __CYGWIN__) && USE_WINDOWS_THREADS
/* Use Windows threads. */
int
pthread_spin_init (pthread_spinlock_t *lock,
int shared_across_processes _GL_UNUSED)
{
glwthread_spin_init (lock);
return 0;
}
int
pthread_spin_lock (pthread_spinlock_t *lock)
{
return glwthread_spin_lock (lock);
}
int
pthread_spin_trylock (pthread_spinlock_t *lock)
{
return glwthread_spin_trylock (lock);
}
int
pthread_spin_unlock (pthread_spinlock_t *lock)
{
return glwthread_spin_unlock (lock);
}
int
pthread_spin_destroy (pthread_spinlock_t *lock)
{
return glwthread_spin_destroy (lock);
}
#elif HAVE_PTHREAD_H
/* Provide workarounds for POSIX threads. */
/* We don't use the C11 <stdatomic.h> (available in GCC >= 4.9) because it would
require to link with -latomic. */
# if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 7)
/* Use GCC built-ins (available in GCC >= 4.7) that operate on the first byte
of the lock.
Documentation:
<https://gcc.gnu.org/onlinedocs/gcc-4.7.0/gcc/_005f_005fatomic-Builtins.html> */
int
pthread_spin_init (pthread_spinlock_t *lock,
int shared_across_processes _GL_UNUSED)
{
__atomic_clear (lock, __ATOMIC_SEQ_CST);
return 0;
}
int
pthread_spin_lock (pthread_spinlock_t *lock)
{
while (__atomic_test_and_set (lock, __ATOMIC_SEQ_CST))
;
return 0;
}
int
pthread_spin_trylock (pthread_spinlock_t *lock)
{
if (__atomic_test_and_set (lock, __ATOMIC_SEQ_CST))
return EBUSY;
return 0;
}
int
pthread_spin_unlock (pthread_spinlock_t *lock)
{
__atomic_clear (lock, __ATOMIC_SEQ_CST);
return 0;
}
int
pthread_spin_destroy (pthread_spinlock_t *lock)
{
return 0;
}
# else
/* Emulate a spin lock through a mutex. */
int
pthread_spin_init (pthread_spinlock_t *lock,
int shared_across_processes _GL_UNUSED)
{
return pthread_mutex_init (lock, NULL);
}
int
pthread_spin_lock (pthread_spinlock_t *lock)
{
return pthread_mutex_lock (lock);
}
int
pthread_spin_trylock (pthread_spinlock_t *lock)
{
return pthread_mutex_trylock (lock);
}
int
pthread_spin_unlock (pthread_spinlock_t *lock)
{
return pthread_mutex_unlock (lock);
}
int
pthread_spin_destroy (pthread_spinlock_t *lock)
{
return pthread_mutex_destroy (lock);
}
# endif
#else
/* Provide a dummy implementation for single-threaded applications. */
int
pthread_spin_init (pthread_spinlock_t *lock _GL_UNUSED,
int shared_across_processes _GL_UNUSED)
{
return 0;
}
int
pthread_spin_lock (pthread_spinlock_t *lock _GL_UNUSED)
{
return 0;
}
int
pthread_spin_trylock (pthread_spinlock_t *lock _GL_UNUSED)
{
return 0;
}
int
pthread_spin_unlock (pthread_spinlock_t *lock _GL_UNUSED)
{
return 0;
}
int
pthread_spin_destroy (pthread_spinlock_t *lock _GL_UNUSED)
{
return 0;
}
#endif
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