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/* Spin locks. L4 version.
Copyright (C) 2000, 2004 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C 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.
The GNU C 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 the GNU C Library; see the file COPYING.LIB. If not,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include <l4.h>
#include <pthread.h>
#include <sched.h>
/* The default for single processor machines; don't spin, it's
pointless. */
#ifndef __PTHREAD_SPIN_COUNT
# define __PTHREAD_SPIN_COUNT 1
#endif
/* The number of times to spin while trying to lock a spin lock object
before yielding the processor. */
int __pthread_spin_count = __PTHREAD_SPIN_COUNT;
/* Lock the spin lock object LOCK. If the lock is held by another
thread spin until it becomes available. */
int
_pthread_spin_lock (__pthread_spinlock_t *lock)
{
l4_time_t timeout;
int i;
/* Start with a small timeout of 2 microseconds, then back off
exponentially. */
timeout = l4_time_period (2);
while (1)
{
for (i = 0; i < __pthread_spin_count; i++)
{
if (__pthread_spin_trylock (lock) == 0)
return 0;
}
l4_sleep (timeout);
timeout = l4_time_mul2 (timeout);
if (timeout == L4_NEVER)
timeout = L4_TIME_PERIOD_MAX;
}
}
weak_alias (_pthread_spin_lock, pthread_spin_lock);
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