spinlock_up.h

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#ifndef __LINUX_SPINLOCK_UP_H
#define __LINUX_SPINLOCK_UP_H

#ifndef __LINUX_SPINLOCK_H
# error "please don't include this file directly"
#endif

#include <asm/processor.h>  /* for cpu_relax() */

/*
 * include/linux/spinlock_up.h - UP-debug version of spinlocks.
 *
 * portions Copyright 2005, Red Hat, Inc., Ingo Molnar
 * Released under the General Public License (GPL).
 *
 * In the debug case, 1 means unlocked, 0 means locked. (the values
 * are inverted, to catch initialization bugs)
 *
 * No atomicity anywhere, we are on UP.
 */

#ifdef CONFIG_DEBUG_SPINLOCK
#define arch_spin_is_locked(x)      ((x)->slock == 0)

static inline void arch_spin_lock(arch_spinlock_t *lock)
{
    lock->slock = 0;
}

static inline void
arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
{
    local_irq_save(flags);
    lock->slock = 0;
}

static inline int arch_spin_trylock(arch_spinlock_t *lock)
{
    char oldval = lock->slock;

    lock->slock = 0;

    return oldval > 0;
}

static inline void arch_spin_unlock(arch_spinlock_t *lock)
{
    lock->slock = 1;
}

/*
 * Read-write spinlocks. No debug version.
 */
#define arch_read_lock(lock)        do { (void)(lock); } while (0)
#define arch_write_lock(lock)       do { (void)(lock); } while (0)
#define arch_read_trylock(lock) ({ (void)(lock); 1; })
#define arch_write_trylock(lock)    ({ (void)(lock); 1; })
#define arch_read_unlock(lock)      do { (void)(lock); } while (0)
#define arch_write_unlock(lock) do { (void)(lock); } while (0)

#else /* DEBUG_SPINLOCK */
#define arch_spin_is_locked(lock)   ((void)(lock), 0)
/* for sched.c and kernel_lock.c: */
# define arch_spin_lock(lock)       do { (void)(lock); } while (0)
# define arch_spin_lock_flags(lock, flags)  do { (void)(lock); } while (0)
# define arch_spin_unlock(lock) do { (void)(lock); } while (0)
# define arch_spin_trylock(lock)    ({ (void)(lock); 1; })
#endif /* DEBUG_SPINLOCK */

#define arch_spin_is_contended(lock)    (((void)(lock), 0))

#define arch_read_can_lock(lock)    (((void)(lock), 1))
#define arch_write_can_lock(lock)   (((void)(lock), 1))

#define arch_spin_unlock_wait(lock) \
        do { cpu_relax(); } while (arch_spin_is_locked(lock))

#endif /* __LINUX_SPINLOCK_UP_H */