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system.h：源码内容
							/*
 *  include/asm-s390/system.h
 *
 *  S390 version
 *    Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
 *    Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com),
 *
 *  Derived from "include/asm-i386/system.h"
 */
#ifndef __ASM_SYSTEM_H
#define __ASM_SYSTEM_H
#include <linux/config.h>
#ifdef __KERNEL__
#include <asm/lowcore.h>
#endif
#include <linux/kernel.h>
#define prepare_to_switch()	do { } while(0)
#define switch_to(prev,next,last) do {                                       
        if (prev == next)                                                    
                break;                                                       
	save_fp_regs(&prev->thread.fp_regs);                                 
	restore_fp_regs(&next->thread.fp_regs);              		     
	last = resume(&prev->thread,&next->thread);                          
} while (0)
struct task_struct;
#define nop() __asm__ __volatile__ ("nop")
#define xchg(ptr,x) 
  ((__typeof__(*(ptr)))__xchg((unsigned long)(x),(void *)(ptr),sizeof(*(ptr))))
extern void __misaligned_u16(void);
extern void __misaligned_u32(void);
extern void __misaligned_u64(void);
static inline unsigned long __xchg(unsigned long x, void * ptr, int size)
{
        switch (size) {
                case 1:
                        asm volatile (
                                "   lghi  1,3n"
                                "   nr    1,%0n"     /* isolate last 2 bits */
                                "   xr    %0,1n"     /* align ptr */
                                "   bras  2,0fn"
                                "   icm   1,8,7(%1)n"   /* for ptr&3 == 0 */
                                "   stcm  0,8,7(%1)n"
                                "   icm   1,4,7(%1)n"   /* for ptr&3 == 1 */
                                "   stcm  0,4,7(%1)n"
                                "   icm   1,2,7(%1)n"   /* for ptr&3 == 2 */
                                "   stcm  0,2,7(%1)n"
                                "   icm   1,1,7(%1)n"   /* for ptr&3 == 3 */
                                "   stcm  0,1,7(%1)n"
                                "0: sll   1,3n"
                                "   la    2,0(1,2)n" /* r2 points to an icm */
                                "   l     0,0(%0)n"  /* get fullword */
                                "1: lr    1,0n"      /* cs loop */
                                "   ex    0,0(2)n"   /* insert x */
                                "   cs    0,1,0(%0)n"
                                "   jl    1bn"
                                "   ex    0,4(2)"     /* store *ptr to x */
                                : "+&a" (ptr) : "a" (&x)
                                : "memory", "cc", "0", "1", "2");
			break;
                case 2:
                        if(((addr_t)ptr)&1)
				__misaligned_u16();
                        asm volatile (
                                "   lghi  1,2n"
                                "   nr    1,%0n"     /* isolate bit 2^1 */
                                "   xr    %0,1n"     /* align ptr */
                                "   bras  2,0fn"
                                "   icm   1,12,6(%1)n"   /* for ptr&2 == 0 */
                                "   stcm  0,12,6(%1)n"
                                "   icm   1,3,2(%1)n"    /* for ptr&2 == 1 */
                                "   stcm  0,3,2(%1)n"
                                "0: sll   1,2n"
                                "   la    2,0(1,2)n" /* r2 points to an icm */
                                "   l     0,0(%0)n"  /* get fullword */
                                "1: lr    1,0n"      /* cs loop */
                                "   ex    0,0(2)n"   /* insert x */
                                "   cs    0,1,0(%0)n"
                                "   jl    1bn"
                                "   ex    0,4(2)"     /* store *ptr to x */
                                : "+&a" (ptr) : "a" (&x)
                                : "memory", "cc", "0", "1", "2");
                        break;
                case 4:
                        if(((addr_t)ptr)&3)
				__misaligned_u32();
                        asm volatile (
                                "    l    0,0(%1)n"
                                "0:  cs   0,%0,0(%1)n"
                                "    jl   0bn"
                                "    lgfr %0,0n"
                                : "+d" (x) : "a" (ptr)
                                : "memory", "cc", "0" );
                        break;
                case 8:
                        if(((addr_t)ptr)&7)
				__misaligned_u64();
                        asm volatile (
                                "    lg  0,0(%1)n"
                                "0:  csg 0,%0,0(%1)n"
                                "    jl  0bn"
                                "    lgr %0,0n"
                                : "+d" (x) : "a" (ptr)
                                : "memory", "cc", "0" );
                        break;
               default:
                        abort();
        }
        return x;
}
/*
 * Force strict CPU ordering.
 * And yes, this is required on UP too when we're talking
 * to devices.
 *
 * This is very similar to the ppc eieio/sync instruction in that is
 * does a checkpoint syncronisation & makes sure that 
 * all memory ops have completed wrt other CPU's ( see 7-15 POP  DJB ).
 */
#define eieio()  __asm__ __volatile__ ("BCR 15,0") 
# define SYNC_OTHER_CORES(x)   eieio() 
#define mb()    eieio()
#define rmb()   eieio()
#define wmb()   eieio()
#define smp_mb()       mb()
#define smp_rmb()      rmb()
#define smp_wmb()      wmb()
#define smp_mb__before_clear_bit()     smp_mb()
#define smp_mb__after_clear_bit()      smp_mb()
#define set_mb(var, value)      do { var = value; mb(); } while (0)
#define set_wmb(var, value)     do { var = value; wmb(); } while (0)
/* interrupt control.. */
#define __sti() ({ 
        unsigned long dummy; 
        __asm__ __volatile__ ( 
                "stosm %0,0x03" : "=m" (dummy) : : "memory"); 
        })
#define __cli() ({ 
        unsigned long flags; 
        __asm__ __volatile__ ( 
                "stnsm %0,0xFC" : "=m" (flags) : : "memory"); 
        flags; 
        })
#define __save_flags(x) 
        __asm__ __volatile__("stosm %0,0" : "=m" (x) : : "memory")
#define __restore_flags(x) 
        __asm__ __volatile__("ssm   %0" : : "m" (x) : "memory")
#define __load_psw(psw) 
        __asm__ __volatile__("lpswe %0" : : "m" (psw) : "cc" );
#define __ctl_load(array, low, high) ({ 
	__asm__ __volatile__ ( 
		"   la    1,%0n" 
		"   bras  2,0fn" 
                "   lctlg 0,0,0(1)n" 
		"0: ex    %1,0(2)" 
		: : "m" (array), "a" (((low)<<4)+(high)) : "1", "2" ); 
	})
#define __ctl_store(array, low, high) ({ 
	__asm__ __volatile__ ( 
		"   la    1,%0n" 
		"   bras  2,0fn" 
		"   stctg 0,0,0(1)n" 
		"0: ex    %1,0(2)" 
		: "=m" (array) : "a" (((low)<<4)+(high)): "1", "2" ); 
	})
#define __ctl_set_bit(cr, bit) ({ 
        __u8 dummy[24]; 
        __asm__ __volatile__ ( 
                "    la    1,%0n"       /* align to 8 byte */ 
                "    aghi  1,7n" 
                "    nill  1,0xfff8n" 
                "    bras  2,0fn"       /* skip indirect insns */ 
                "    stctg 0,0,0(1)n" 
                "    lctlg 0,0,0(1)n" 
                "0:  ex    %1,0(2)n"    /* execute stctl */ 
                "    lg    0,0(1)n" 
                "    ogr   0,%2n"       /* set the bit */ 
                "    stg   0,0(1)n" 
                "1:  ex    %1,6(2)"      /* execute lctl */ 
                : "=m" (dummy) : "a" (cr*17), "a" (1L<<(bit)) 
                : "cc", "0", "1", "2"); 
        })
#define __ctl_clear_bit(cr, bit) ({ 
        __u8 dummy[24]; 
        __asm__ __volatile__ ( 
                "    la    1,%0n"       /* align to 8 byte */ 
                "    aghi  1,7n" 
                "    nill  1,0xfff8n" 
                "    bras  2,0fn"       /* skip indirect insns */ 
                "    stctg 0,0,0(1)n" 
                "    lctlg 0,0,0(1)n" 
                "0:  ex    %1,0(2)n"    /* execute stctl */ 
                "    lg    0,0(1)n" 
                "    ngr   0,%2n"       /* set the bit */ 
                "    stg   0,0(1)n" 
                "1:  ex    %1,6(2)"      /* execute lctl */ 
                : "=m" (dummy) : "a" (cr*17), "a" (~(1L<<(bit))) 
                : "cc", "0", "1", "2"); 
        })
/* For spinlocks etc */
#define local_irq_save(x)	((x) = __cli())
#define local_irq_restore(x)	__restore_flags(x)
#define local_irq_disable()	__cli()
#define local_irq_enable()	__sti()
#ifdef CONFIG_SMP
extern void __global_cli(void);
extern void __global_sti(void);
extern unsigned long __global_save_flags(void);
extern void __global_restore_flags(unsigned long);
#define cli() __global_cli()
#define sti() __global_sti()
#define save_flags(x) ((x)=__global_save_flags())
#define restore_flags(x) __global_restore_flags(x)
extern void smp_ctl_set_bit(int cr, int bit);
extern void smp_ctl_clear_bit(int cr, int bit);
#define ctl_set_bit(cr, bit) smp_ctl_set_bit(cr, bit)
#define ctl_clear_bit(cr, bit) smp_ctl_clear_bit(cr, bit)
#else
#define cli() __cli()
#define sti() __sti()
#define save_flags(x) __save_flags(x)
#define restore_flags(x) __restore_flags(x)
#define ctl_set_bit(cr, bit) __ctl_set_bit(cr, bit)
#define ctl_clear_bit(cr, bit) __ctl_clear_bit(cr, bit)
#endif
#ifdef __KERNEL__
extern struct task_struct *resume(void *,void *);
extern int save_fp_regs1(s390_fp_regs *fpregs);
extern void save_fp_regs(s390_fp_regs *fpregs);
extern int restore_fp_regs1(s390_fp_regs *fpregs);
extern void restore_fp_regs(s390_fp_regs *fpregs);
#endif
#endif

						