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 #ifndef __ASSEMBLY__
  18
  19 #include <linux/types.h>
  20 #include <linux/irqflags.h>
  21
  22 #include <asm/cmpxchg-local.h>
  23 #include <asm/cmpxchg.h>
  24
  25 struct task_struct;
  26
  27 /* context switching is now performed out-of-line in switch_to.S */
  28 extern 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().  */
  76 extern void __xchg_called_with_bad_pointer(void);
  77
  78 static inline
  79 unsigned 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
 139 #endif /* !__ASSEMBLY__ */
 140
 141 #endif /* __ASM_GENERIC_SYSTEM_H */