嵌入式Linux

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atomic.h：源码内容
							#ifndef __ARCH_S390_ATOMIC__
#define __ARCH_S390_ATOMIC__
/*
 *  include/asm-s390/atomic.h
 *
 *  S390 version
 *    Copyright (C) 1999,2000 IBM Deutschland Entwicklung GmbH, IBM Corporation
 *    Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com),
 *               Denis Joseph Barrow
 *
 *  Derived from "include/asm-i386/bitops.h"
 *    Copyright (C) 1992, Linus Torvalds
 *
 */
/*
 * Atomic operations that C can't guarantee us.  Useful for
 * resource counting etc..
 * S390 uses 'Compare And Swap' for atomicity in SMP enviroment
 */
typedef struct { volatile int counter; } __attribute__ ((aligned (4))) atomic_t;
#define ATOMIC_INIT(i)  { (i) }
#define atomic_eieio()          __asm__ __volatile__ ("BCR 15,0")
#define __CS_LOOP(old_val, new_val, ptr, op_val, op_string)		
        __asm__ __volatile__("   l     %0,0(%2)n"			
                             "0: lr    %1,%0n"				
                             op_string "  %1,%3n"			
                             "   cs    %0,%1,0(%2)n"			
                             "   jl    0b"				
                             : "=&d" (old_val), "=&d" (new_val)		
			     : "a" (ptr), "d" (op_val) : "cc" );
static __inline__ int atomic_read(atomic_t *v)
{
        int retval;
        __asm__ __volatile__("bcr      15,0nt"
                             "l        %0,%1"
                             : "=d" (retval) : "m" (*v) );
        return retval;
}
static __inline__ void atomic_set(atomic_t *v, int i)
{
        __asm__ __volatile__("st  %1,%0nt"
                             "bcr 15,0"
                             : "=m" (*v) : "d" (i) );
}
static __inline__ void atomic_add(int i, atomic_t *v)
{
	int old_val, new_val;
	__CS_LOOP(old_val, new_val, v, i, "ar");
}
static __inline__ int atomic_add_return (int i, atomic_t *v)
{
	int old_val, new_val;
	__CS_LOOP(old_val, new_val, v, i, "ar");
	return new_val;
}
static __inline__ int atomic_add_negative(int i, atomic_t *v)
{
	int old_val, new_val;
        __CS_LOOP(old_val, new_val, v, i, "ar");
        return new_val < 0;
}
static __inline__ void atomic_sub(int i, atomic_t *v)
{
	int old_val, new_val;
	__CS_LOOP(old_val, new_val, v, i, "sr");
}
static __inline__ void atomic_inc(volatile atomic_t *v)
{
	int old_val, new_val;
	__CS_LOOP(old_val, new_val, v, 1, "ar");
}
static __inline__ int atomic_inc_return(volatile atomic_t *v)
{
	int old_val, new_val;
	__CS_LOOP(old_val, new_val, v, 1, "ar");
        return new_val;
}
static __inline__ int atomic_inc_and_test(volatile atomic_t *v)
{
	int old_val, new_val;
	__CS_LOOP(old_val, new_val, v, 1, "ar");
	return new_val != 0;
}
static __inline__ void atomic_dec(volatile atomic_t *v)
{
	int old_val, new_val;
	__CS_LOOP(old_val, new_val, v, 1, "sr");
}
static __inline__ int atomic_dec_return(volatile atomic_t *v)
{
	int old_val, new_val;
	__CS_LOOP(old_val, new_val, v, 1, "sr");
        return new_val;
}
static __inline__ int atomic_dec_and_test(volatile atomic_t *v)
{
	int old_val, new_val;
	__CS_LOOP(old_val, new_val, v, 1, "sr");
        return new_val == 0;
}
static __inline__ void atomic_clear_mask(unsigned long mask, atomic_t *v)
{
	int old_val, new_val;
	__CS_LOOP(old_val, new_val, v, ~mask, "nr");
}
static __inline__ void atomic_set_mask(unsigned long mask, atomic_t *v)
{
	int old_val, new_val;
	__CS_LOOP(old_val, new_val, v, mask, "or");
}
/*
  returns 0  if expected_oldval==value in *v ( swap was successful )
  returns 1  if unsuccessful.
*/
static __inline__ int
atomic_compare_and_swap(int expected_oldval,int new_val,atomic_t *v)
{
        int retval;
        __asm__ __volatile__(
                "  lr   0,%2n"
                "  cs   0,%3,0(%1)n"
                "  ipm  %0n"
                "  srl  %0,28n"
                "0:"
                : "=&d" (retval)
                : "a" (v), "d" (expected_oldval) , "d" (new_val)
                : "0", "cc");
        return retval;
}
/*
  Spin till *v = expected_oldval then swap with newval.
 */
static __inline__ void
atomic_compare_and_swap_spin(int expected_oldval,int new_val,atomic_t *v)
{
        __asm__ __volatile__(
                "0: lr  0,%1n"
                "   cs  0,%2,0(%0)n"
                "   jl  0bn"
                : : "a" (v), "d" (expected_oldval) , "d" (new_val)
                : "cc", "0" );
}
#define atomic_compare_and_swap_debug(where,from,to) 
if (atomic_compare_and_swap ((from), (to), (where))) {
	printk (KERN_WARNING"%s/%d atomic counter:%s couldn't be changed from %d(%s) to %d(%s), was %dn",
		__FILE__,__LINE__,#where,(from),#from,(to),#to,atomic_read (where));
        atomic_set(where,(to));
}
#define smp_mb__before_atomic_dec()	smp_mb()
#define smp_mb__after_atomic_dec()	smp_mb()
#define smp_mb__before_atomic_inc()	smp_mb()
#define smp_mb__after_atomic_inc()	smp_mb()
#endif                                 /* __ARCH_S390_ATOMIC __            */

						