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 #include <asm/cmpxchg.h>
  25
  26 struct task_struct;
  27
  28 /* context switching is now performed out-of-line in switch_to.S */
  29 extern struct task_struct *__switch_to(struct task_struct *,
  30                 struct task_struct *);
  31 #define switch_to(prev, next, last)                                     \
  32         do {                                                            \
  33                 ((last) = __switch_to((prev), (next)));                 \
  34         } while (0)
  35
  36 #define arch_align_stack(x) (x)
  37
  38 #define nop() asm volatile ("nop")
  39
  40 #endif /* !__ASSEMBLY__ */
  41
  42 /*
  43  * Force strict CPU ordering.
  44  * And yes, this is required on UP too when we're talking
  45  * to devices.
  46  *
  47  * This implementation only contains a compiler barrier.
  48  */
  49
  50 #define mb()    asm volatile ("": : :"memory")
  51 #define rmb()   mb()
  52 #define wmb()   asm volatile ("": : :"memory")
  53
  54 #ifdef CONFIG_SMP
  55 #define smp_mb()        mb()
  56 #define smp_rmb()       rmb()
  57 #define smp_wmb()       wmb()
  58 #else
  59 #define smp_mb()        barrier()
  60 #define smp_rmb()       barrier()
  61 #define smp_wmb()       barrier()
  62 #endif
  63
  64 #define set_mb(var, value)  do { var = value;  mb(); } while (0)
  65 #define set_wmb(var, value) do { var = value; wmb(); } while (0)
  66
  67 #define read_barrier_depends()          do {} while (0)
  68 #define smp_read_barrier_depends()      do {} while (0)
  69
  70 /*
  71  * we make sure local_irq_enable() doesn't cause priority inversion
  72  */
  73 #ifndef __ASSEMBLY__
  74
  75 /* This function doesn't exist, so you'll get a linker error
  76  *    if something tries to do an invalid xchg().  */
  77 extern void __xchg_called_with_bad_pointer(void);
  78
  79 static inline
  80 unsigned long __xchg(unsigned long x, volatile void *ptr, int size)
  81 {
  82         unsigned long ret, flags;
  83
  84         switch (size) {
  85         case 1:
  86 #ifdef __xchg_u8
  87                 return __xchg_u8(x, ptr);
  88 #else
  89                 local_irq_save(flags);
  90                 ret = *(volatile u8 *)ptr;
  91                 *(volatile u8 *)ptr = x;
  92                 local_irq_restore(flags);
  93                 return ret;
  94 #endif /* __xchg_u8 */
  95
  96         case 2:
  97 #ifdef __xchg_u16
  98                 return __xchg_u16(x, ptr);
  99 #else
 100                 local_irq_save(flags);
 101                 ret = *(volatile u16 *)ptr;
 102                 *(volatile u16 *)ptr = x;
 103                 local_irq_restore(flags);
 104                 return ret;
 105 #endif /* __xchg_u16 */
 106
 107         case 4:
 108 #ifdef __xchg_u32
 109                 return __xchg_u32(x, ptr);
 110 #else
 111                 local_irq_save(flags);
 112                 ret = *(volatile u32 *)ptr;
 113                 *(volatile u32 *)ptr = x;
 114                 local_irq_restore(flags);
 115                 return ret;
 116 #endif /* __xchg_u32 */
 117
 118 #ifdef CONFIG_64BIT
 119         case 8:
 120 #ifdef __xchg_u64
 121                 return __xchg_u64(x, ptr);
 122 #else
 123                 local_irq_save(flags);
 124                 ret = *(volatile u64 *)ptr;
 125                 *(volatile u64 *)ptr = x;
 126                 local_irq_restore(flags);
 127                 return ret;
 128 #endif /* __xchg_u64 */
 129 #endif /* CONFIG_64BIT */
 130
 131         default:
 132                 __xchg_called_with_bad_pointer();
 133                 return x;
 134         }
 135 }
 136
 137 #define xchg(ptr, x) \
 138         ((__typeof__(*(ptr))) __xchg((unsigned long)(x), (ptr), sizeof(*(ptr))))
 139
 140 #endif /* !__ASSEMBLY__ */
 141
 142 #endif /* __KERNEL__ */
 143 #endif /* __ASM_GENERIC_SYSTEM_H */