1. 根目录:
2. arch
3. m68k
4. include
5. asm
6. system_no.h

#ifndef _M68KNOMMU_SYSTEM_H
#define _M68KNOMMU_SYSTEM_H

#include <linux/linkage.h>
#include <linux/irqflags.h>
#include <asm/segment.h>
#include <asm/entry.h>

/*
 * switch_to(n) should switch tasks to task ptr, first checking that
 * ptr isn't the current task, in which case it does nothing.  This
 * also clears the TS-flag if the task we switched to has used the
 * math co-processor latest.
 */
/*
 * switch_to() saves the extra registers, that are not saved
 * automatically by SAVE_SWITCH_STACK in resume(), ie. d0-d5 and
 * a0-a1. Some of these are used by schedule() and its predecessors
 * and so we might get see unexpected behaviors when a task returns
 * with unexpected register values.
 *
 * syscall stores these registers itself and none of them are used
 * by syscall after the function in the syscall has been called.
 *
 * Beware that resume now expects *next to be in d1 and the offset of
 * tss to be in a1. This saves a few instructions as we no longer have
 * to push them onto the stack and read them back right after.
 *
 * 02/17/96 - Jes Sorensen (jds@kom.auc.dk)
 *
 * Changed 96/09/19 by Andreas Schwab
 * pass prev in a0, next in a1, offset of tss in d1, and whether
 * the mm structures are shared in d2 (to avoid atc flushing).
 */
asmlinkage void resume(void);
#define switch_to(prev,next,last)				\
{								\
  void *_last;							\
  __asm__ __volatile__(						\
  	"movel	%1, %%a0\n\t"					\
	"movel	%2, %%a1\n\t"					\
	"jbsr resume\n\t"					\
	"movel	%%d1, %0\n\t"					\
       : "=d" (_last)						\
       : "d" (prev), "d" (next)					\
       : "cc", "d0", "d1", "d2", "d3", "d4", "d5", "a0", "a1");	\
  (last) = _last;						\
}

#define iret() __asm__ __volatile__ ("rte": : :"memory", "sp", "cc")

/*
 * Force strict CPU ordering.
 * Not really required on m68k...
 */
#define nop()  asm volatile ("nop"::)
#define mb()   asm volatile (""   : : :"memory")
#define rmb()  asm volatile (""   : : :"memory")
#define wmb()  asm volatile (""   : : :"memory")
#define set_mb(var, value)	({ (var) = (value); wmb(); })

#define smp_mb()	barrier()
#define smp_rmb()	barrier()
#define smp_wmb()	barrier()
#define smp_read_barrier_depends()	do { } while(0)

#define read_barrier_depends()  ((void)0)

#define xchg(ptr,x) ((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr))))

struct __xchg_dummy { unsigned long a[100]; };
#define __xg(x) ((volatile struct __xchg_dummy *)(x))

#ifndef CONFIG_RMW_INSNS
static inline unsigned long __xchg(unsigned long x, volatile void * ptr, int size)
{
  unsigned long tmp, flags;

  local_irq_save(flags);

  switch (size) {
  case 1:
    __asm__ __volatile__
    ("moveb %2,%0\n\t"
     "moveb %1,%2"
    : "=&d" (tmp) : "d" (x), "m" (*__xg(ptr)) : "memory");
    break;
  case 2:
    __asm__ __volatile__
    ("movew %2,%0\n\t"
     "movew %1,%2"
    : "=&d" (tmp) : "d" (x), "m" (*__xg(ptr)) : "memory");
    break;
  case 4:
    __asm__ __volatile__
    ("movel %2,%0\n\t"
     "movel %1,%2"
    : "=&d" (tmp) : "d" (x), "m" (*__xg(ptr)) : "memory");
    break;
  }
  local_irq_restore(flags);
  return tmp;
}
#else
static inline unsigned long __xchg(unsigned long x, volatile void * ptr, int size)
{
	switch (size) {
	    case 1:
		__asm__ __volatile__
			("moveb %2,%0\n\t"
			 "1:\n\t"
			 "casb %0,%1,%2\n\t"
			 "jne 1b"
			 : "=&d" (x) : "d" (x), "m" (*__xg(ptr)) : "memory");
		break;
	    case 2:
		__asm__ __volatile__
			("movew %2,%0\n\t"
			 "1:\n\t"
			 "casw %0,%1,%2\n\t"
			 "jne 1b"
			 : "=&d" (x) : "d" (x), "m" (*__xg(ptr)) : "memory");
		break;
	    case 4:
		__asm__ __volatile__
			("movel %2,%0\n\t"
			 "1:\n\t"
			 "casl %0,%1,%2\n\t"
			 "jne 1b"
			 : "=&d" (x) : "d" (x), "m" (*__xg(ptr)) : "memory");
		break;
	}
	return x;
}
#endif

#include <asm-generic/cmpxchg-local.h>

/*
 * cmpxchg_local and cmpxchg64_local are atomic wrt current CPU. Always make
 * them available.
 */
#define cmpxchg_local(ptr, o, n)				  	       \
	((__typeof__(*(ptr)))__cmpxchg_local_generic((ptr), (unsigned long)(o),\
			(unsigned long)(n), sizeof(*(ptr))))
#define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))

#include <asm-generic/cmpxchg.h>

#define arch_align_stack(x) (x)


#endif /* _M68KNOMMU_SYSTEM_H */