/*
* ia64 implementation of the mutex fastpath.
*
* Copyright (C) 2006 Ken Chen <[email protected]>
*
*/

#ifndef _ASM_MUTEX_H
#define _ASM_MUTEX_H

/**
* __mutex_fastpath_lock - try to take the lock by moving the count
* from 1 to a 0 value
* @count: pointer of type atomic_t
* @fail_fn: function to call if the original value was not 1
*
* Change the count from 1 to a value lower than 1, and call <fail_fn> if
* it wasn't 1 originally. This function MUST leave the value lower than
* 1 even when the "1" assertion wasn't true.
*/
static inline void
__mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *))
{
if (unlikely(ia64_fetchadd4_acq(count, -1) != 1))
fail_fn(count);
}

/**
* __mutex_fastpath_lock_retval - try to take the lock by moving the count
* from 1 to a 0 value
* @count: pointer of type atomic_t
*
* Change the count from 1 to a value lower than 1. This function returns 0
* if the fastpath succeeds, or -1 otherwise.
*/
static inline int
__mutex_fastpath_lock_retval(atomic_t *count)
{
if (unlikely(ia64_fetchadd4_acq(count, -1) != 1))
return -1;
return 0;
}

/**
* __mutex_fastpath_unlock - try to promote the count from 0 to 1
* @count: pointer of type atomic_t
* @fail_fn: function to call if the original value was not 0
*
* Try to promote the count from 0 to 1. If it wasn't 0, call <fail_fn>.
* In the failure case, this function is allowed to either set the value to
* 1, or to set it to a value lower than 1.
*
* If the implementation sets it to a value of lower than 1, then the
* __mutex_slowpath_needs_to_unlock() macro needs to return 1, it needs
* to return 0 otherwise.
*/
static inline void
__mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
{
int ret = ia64_fetchadd4_rel(count, 1);
if (unlikely(ret < 0))
fail_fn(count);
}

#define __mutex_slowpath_needs_to_unlock() 1

/**
* __mutex_fastpath_trylock - try to acquire the mutex, without waiting
*
* @count: pointer of type atomic_t
* @fail_fn: fallback function
*
* Change the count from 1 to a value lower than 1, and return 0 (failure)
* if it wasn't 1 originally, or return 1 (success) otherwise. This function
* MUST leave the value lower than 1 even when the "1" assertion wasn't true.
* Additionally, if the value was < 0 originally, this function must not leave
* it to 0 on failure.
*
* If the architecture has no effective trylock variant, it should call the
* <fail_fn> spinlock-based trylock variant unconditionally.
*/
static inline int
__mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
{
if (cmpxchg_acq(count, 1, 0) == 1)
return 1;
return 0;
}

#endif