atomic.h

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/*
 * Atomic operations that C can't guarantee us.  Useful for
 * resource counting etc..
 *
 * But use these as seldom as possible since they are much more slower
 * than regular operations.
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 1996, 1997, 2000 by Ralf Baechle
 */
#ifndef __ASM_ATOMIC_H
#define __ASM_ATOMIC_H

#include <linux/config.h>

typedef struct { volatile int counter; } atomic_t;

#ifdef __KERNEL__
#define ATOMIC_INIT(i)    { (i) }

/*
 * atomic_read - read atomic variable
 * @v: pointer of type atomic_t
 *
 * Atomically reads the value of @v.  Note that the guaranteed
 * useful range of an atomic_t is only 24 bits.
 */
#define atomic_read(v)	((v)->counter)

/*
 * atomic_set - set atomic variable
 * @v: pointer of type atomic_t
 * @i: required value
 *
 * Atomically sets the value of @v to @i.  Note that the guaranteed
 * useful range of an atomic_t is only 24 bits.
 */
#define atomic_set(v,i)	((v)->counter = (i))

#ifndef CONFIG_CPU_HAS_LLSC

#include <asm/system.h>

/*
 * The MIPS I implementation is only atomic with respect to
 * interrupts.  R3000 based multiprocessor machines are rare anyway ...
 *
 * atomic_add - add integer to atomic variable
 * @i: integer value to add
 * @v: pointer of type atomic_t
 *
 * Atomically adds @i to @v.  Note that the guaranteed useful range
 * of an atomic_t is only 24 bits.
 */
extern __inline__ void atomic_add(int i, atomic_t * v)
{
	int	flags;

	save_flags(flags);
	cli();
	v->counter += i;
	restore_flags(flags);
}

/*
 * atomic_sub - subtract the atomic variable
 * @i: integer value to subtract
 * @v: pointer of type atomic_t
 *
 * Atomically subtracts @i from @v.  Note that the guaranteed
 * useful range of an atomic_t is only 24 bits.
 */
extern __inline__ void atomic_sub(int i, atomic_t * v)
{
	int	flags;

	save_flags(flags);
	cli();
	v->counter -= i;
	restore_flags(flags);
}

extern __inline__ int atomic_add_return(int i, atomic_t * v)
{
	int	temp, flags;

	save_flags(flags);
	cli();
	temp = v->counter;
	temp += i;
	v->counter = temp;
	restore_flags(flags);

	return temp;
}

extern __inline__ int atomic_sub_return(int i, atomic_t * v)
{
	int	temp, flags;

	save_flags(flags);
	cli();
	temp = v->counter;
	temp -= i;
	v->counter = temp;
	restore_flags(flags);

	return temp;
}

#else

/*
 * ... while for MIPS II and better we can use ll/sc instruction.  This
 * implementation is SMP safe ...
 */

/*
 * atomic_add - add integer to atomic variable
 * @i: integer value to add
 * @v: pointer of type atomic_t
 *
 * Atomically adds @i to @v.  Note that the guaranteed useful range
 * of an atomic_t is only 24 bits.
 */
extern __inline__ void atomic_add(int i, atomic_t * v)
{
	unsigned long temp;

	__asm__ __volatile__(
		"1:   ll      %0, %1      # atomic_add\n"
		"     addu    %0, %2                  \n"
		"     sc      %0, %1                  \n"
		"     beqz    %0, 1b                  \n"
		: "=&r" (temp), "=m" (v->counter)
		: "Ir" (i), "m" (v->counter));
}

/*
 * atomic_sub - subtract the atomic variable
 * @i: integer value to subtract
 * @v: pointer of type atomic_t
 *
 * Atomically subtracts @i from @v.  Note that the guaranteed
 * useful range of an atomic_t is only 24 bits.
 */
extern __inline__ void atomic_sub(int i, atomic_t * v)
{
	unsigned long temp;

	__asm__ __volatile__(
		"1:   ll      %0, %1      # atomic_sub\n"
		"     subu    %0, %2                  \n"
		"     sc      %0, %1                  \n"
		"     beqz    %0, 1b                  \n"
		: "=&r" (temp), "=m" (v->counter)
		: "Ir" (i), "m" (v->counter));
}

/*
 * Same as above, but return the result value
 */
extern __inline__ int atomic_add_return(int i, atomic_t * v)
{
	unsigned long temp, result;

	__asm__ __volatile__(
		".set push               # atomic_add_return\n"
		".set noreorder                             \n"
		"1:   ll      %1, %2                        \n"
		"     addu    %0, %1, %3                    \n"
		"     sc      %0, %2                        \n"
		"     beqz    %0, 1b                        \n"
		"     addu    %0, %1, %3                    \n"
		".set pop                                   \n"
		: "=&r" (result), "=&r" (temp), "=m" (v->counter)
		: "Ir" (i), "m" (v->counter)
		: "memory");

	return result;
}

extern __inline__ int atomic_sub_return(int i, atomic_t * v)
{
	unsigned long temp, result;

	__asm__ __volatile__(
		".set push                                   \n"
		".set noreorder           # atomic_sub_return\n"
		"1:   ll    %1, %2                           \n"
		"     subu  %0, %1, %3                       \n"
		"     sc    %0, %2                           \n"
		"     beqz  %0, 1b                           \n"
		"     subu  %0, %1, %3                       \n"
		".set pop                                    \n"
		: "=&r" (result), "=&r" (temp), "=m" (v->counter)
		: "Ir" (i), "m" (v->counter)
		: "memory");

	return result;
}
#endif

#define atomic_dec_return(v) atomic_sub_return(1,(v))
#define atomic_inc_return(v) atomic_add_return(1,(v))

/*
 * atomic_sub_and_test - subtract value from variable and test result
 * @i: integer value to subtract
 * @v: pointer of type atomic_t
 *
 * Atomically subtracts @i from @v and returns
 * true if the result is zero, or false for all
 * other cases.  Note that the guaranteed
 * useful range of an atomic_t is only 24 bits.
 */
#define atomic_sub_and_test(i,v) (atomic_sub_return((i), (v)) == 0)

/*
 * atomic_inc_and_test - increment and test
 * @v: pointer of type atomic_t
 *
 * Atomically increments @v by 1
 * and returns true if the result is zero, or false for all
 * other cases.  Note that the guaranteed
 * useful range of an atomic_t is only 24 bits.
 */
#define atomic_inc_and_test(v) (atomic_inc_return(1, (v)) == 0)

/*
 * atomic_dec_and_test - decrement by 1 and test
 * @v: pointer of type atomic_t
 *
 * Atomically decrements @v by 1 and
 * returns true if the result is 0, or false for all other
 * cases.  Note that the guaranteed
 * useful range of an atomic_t is only 24 bits.
 */
#define atomic_dec_and_test(v) (atomic_sub_return(1, (v)) == 0)

/*
 * atomic_inc - increment atomic variable
 * @v: pointer of type atomic_t
 *
 * Atomically increments @v by 1.  Note that the guaranteed
 * useful range of an atomic_t is only 24 bits.
 */
#define atomic_inc(v) atomic_add(1,(v))

/*
 * atomic_dec - decrement and test
 * @v: pointer of type atomic_t
 *
 * Atomically decrements @v by 1.  Note that the guaranteed
 * useful range of an atomic_t is only 24 bits.
 */
#define atomic_dec(v) atomic_sub(1,(v))

/*
 * atomic_add_negative - add and test if negative
 * @v: pointer of type atomic_t
 * @i: integer value to add
 *
 * Atomically adds @i to @v and returns true
 * if the result is negative, or false when
 * result is greater than or equal to zero.  Note that the guaranteed
 * useful range of an atomic_t is only 24 bits.
 *
 * Currently not implemented for MIPS.
 */

/* Atomic operations are already serializing */
#define smp_mb__before_atomic_dec()	barrier()
#define smp_mb__after_atomic_dec()	barrier()
#define smp_mb__before_atomic_inc()	barrier()
#define smp_mb__after_atomic_inc()	barrier()

#endif /* defined(__KERNEL__) */

#endif /* __ASM_ATOMIC_H */