LXR linux/include/asm-generic/system.h

   1/* Generic system definitions, based on MN10300 definitions.
   2 *
   3 * It should be possible to use these on really simple architectures,
   4 * but it serves more as a starting point for new ports.
   5 *
   6 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   7 * Written by David Howells (dhowells@redhat.com)
   8 *
   9 * This program is free software; you can redistribute it and/or
  10 * modify it under the terms of the GNU General Public Licence
  11 * as published by the Free Software Foundation; either version
  12 * 2 of the Licence, or (at your option) any later version.
  13 */
  14#ifndef __ASM_GENERIC_SYSTEM_H
  15#define __ASM_GENERIC_SYSTEM_H
  16
  17#ifdef __KERNEL__
  18#ifndef __ASSEMBLY__
  19
  20#include <linux/types.h>
  21#include <linux/irqflags.h>
  22
  23#include <asm/cmpxchg-local.h>
  24
  25struct task_struct;
  26
  27/* context switching is now performed out-of-line in switch_to.S */
  28extern struct task_struct *__switch_to(struct task_struct *,
  29                struct task_struct *);
  30#define switch_to(prev, next, last)                                     \
  31        do {                                                            \
  32                ((last) = __switch_to((prev), (next)));                 \
  33        } while (0)
  34
  35#define arch_align_stack(x) (x)
  36
  37#define nop() asm volatile ("nop")
  38
  39#endif /* !__ASSEMBLY__ */
  40
  41/*
  42 * Force strict CPU ordering.
  43 * And yes, this is required on UP too when we're talking
  44 * to devices.
  45 *
  46 * This implementation only contains a compiler barrier.
  47 */
  48
  49#define mb()    asm volatile ("": : :"memory")
  50#define rmb()   mb()
  51#define wmb()   asm volatile ("": : :"memory")
  52
  53#ifdef CONFIG_SMP
  54#define smp_mb()        mb()
  55#define smp_rmb()       rmb()
  56#define smp_wmb()       wmb()
  57#else
  58#define smp_mb()        barrier()
  59#define smp_rmb()       barrier()
  60#define smp_wmb()       barrier()
  61#endif
  62
  63#define set_mb(var, value)  do { var = value;  mb(); } while (0)
  64#define set_wmb(var, value) do { var = value; wmb(); } while (0)
  65
  66#define read_barrier_depends()          do {} while (0)
  67#define smp_read_barrier_depends()      do {} while (0)
  68
  69/*
  70 * we make sure local_irq_enable() doesn't cause priority inversion
  71 */
  72#ifndef __ASSEMBLY__
  73
  74/* This function doesn't exist, so you'll get a linker error
  75 *    if something tries to do an invalid xchg().  */
  76extern void __xchg_called_with_bad_pointer(void);
  77
  78static inline
  79unsigned long __xchg(unsigned long x, volatile void *ptr, int size)
  80{
  81        unsigned long ret, flags;
  82
  83        switch (size) {
  84        case 1:
  85#ifdef __xchg_u8
  86                return __xchg_u8(x, ptr);
  87#else
  88                local_irq_save(flags);
  89                ret = *(volatile u8 *)ptr;
  90                *(volatile u8 *)ptr = x;
  91                local_irq_restore(flags);
  92                return ret;
  93#endif /* __xchg_u8 */
  94
  95        case 2:
  96#ifdef __xchg_u16
  97                return __xchg_u16(x, ptr);
  98#else
  99                local_irq_save(flags);
 100                ret = *(volatile u16 *)ptr;
 101                *(volatile u16 *)ptr = x;
 102                local_irq_restore(flags);
 103                return ret;
 104#endif /* __xchg_u16 */
 105
 106        case 4:
 107#ifdef __xchg_u32
 108                return __xchg_u32(x, ptr);
 109#else
 110                local_irq_save(flags);
 111                ret = *(volatile u32 *)ptr;
 112                *(volatile u32 *)ptr = x;
 113                local_irq_restore(flags);
 114                return ret;
 115#endif /* __xchg_u32 */
 116
 117#ifdef CONFIG_64BIT
 118        case 8:
 119#ifdef __xchg_u64
 120                return __xchg_u64(x, ptr);
 121#else
 122                local_irq_save(flags);
 123                ret = *(volatile u64 *)ptr;
 124                *(volatile u64 *)ptr = x;
 125                local_irq_restore(flags);
 126                return ret;
 127#endif /* __xchg_u64 */
 128#endif /* CONFIG_64BIT */
 129
 130        default:
 131                __xchg_called_with_bad_pointer();
 132                return x;
 133        }
 134}
 135
 136#define xchg(ptr, x) \
 137        ((__typeof__(*(ptr))) __xchg((unsigned long)(x), (ptr), sizeof(*(ptr))))
 138
 139static inline unsigned long __cmpxchg(volatile unsigned long *m,
 140                                      unsigned long old, unsigned long new)
 141{
 142        unsigned long retval;
 143        unsigned long flags;
 144
 145        local_irq_save(flags);
 146        retval = *m;
 147        if (retval == old)
 148                *m = new;
 149        local_irq_restore(flags);
 150        return retval;
 151}
 152
 153#define cmpxchg(ptr, o, n)                                      \
 154        ((__typeof__(*(ptr))) __cmpxchg((unsigned long *)(ptr), \
 155                                        (unsigned long)(o),     \
 156                                        (unsigned long)(n)))
 157
 158#endif /* !__ASSEMBLY__ */
 159
 160#endif /* __KERNEL__ */
 161#endif /* __ASM_GENERIC_SYSTEM_H */
 162