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/*
* Copyright (c) 2012, 2013 Richard Braun.
*
* 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 3 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 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 <http://www.gnu.org/licenses/>.
*
*
* This implementation relies on the availability of hardware compare-and-swap
* support. It means that almost all spinlock operations imply a full memory
* barrier. Users must not rely on this behaviour as it could change in the
* future.
*/
#ifndef _KERN_SPINLOCK_I_H
#define _KERN_SPINLOCK_I_H
#include <kern/assert.h>
#include <machine/atomic.h>
#include <machine/cpu.h>
struct spinlock {
unsigned long locked;
};
/*
* Return 0 on success, 1 if busy.
*/
static inline int
spinlock_tryacquire(struct spinlock *lock)
{
return atomic_cas(&lock->locked, 0, 1);
}
static inline void
spinlock_acquire(struct spinlock *lock)
{
while (spinlock_tryacquire(lock))
cpu_pause();
}
static inline void
spinlock_release(struct spinlock *lock)
{
unsigned long locked;
locked = atomic_swap(&lock->locked, 0);
assert(locked);
}
#endif /* _KERN_SPINLOCK_I_H */
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