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Commit a454c2f3 authored by Kenneth W Chen's avatar Kenneth W Chen Committed by Tony Luck
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[IA64] implement ia64 specific mutex primitives 



Implement ia64 optimized mutex primitives.  It properly uses
acquire/release memory ordering semantics in lock/unlock path.
2nd version making them all static inline functions.

Signed-off-by: default avatarKen Chen <kenneth.w.chen@intel.com>
Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
parent 3ee68c4a

include/asm-ia64/mutex.h

+88 −5
Original line number Diff line number Diff line 
/*

 * Pull in the generic implementation for the mutex fastpath.

 * ia64 implementation of the mutex fastpath.

 *

 * TODO: implement optimized primitives instead, or leave the generic

 * implementation in place, or pick the atomic_xchg() based generic

 * implementation. (see asm-generic/mutex-xchg.h for details)

 * Copyright (C) 2006 Ken Chen <kenneth.w.chen@intel.com>

 *

 */



#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

 *  @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 returns 0 if the fastpath succeeds,

 * or anything the slow path function returns.

 */

static inline int

__mutex_fastpath_lock_retval(atomic_t *count, int (*fail_fn)(atomic_t *))

{

	if (unlikely(ia64_fetchadd4_acq(count, -1) != 1))

		return fail_fn(count);

	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 (likely(cmpxchg_acq(count, 1, 0)) == 1)

		return 1;

	return 0;

}



#include <asm-generic/mutex-dec.h>
 
#endif