include/asm-generic/cmpxchg.h

   1 /*
   2  * Generic UP xchg and cmpxchg using interrupt disablement.  Does not
   3  * support SMP.
   4  */
   5
   6 #ifndef __ASM_GENERIC_CMPXCHG_H
   7 #define __ASM_GENERIC_CMPXCHG_H
   8
   9 #ifdef CONFIG_SMP
  10 #error "Cannot use generic cmpxchg on SMP"
  11 #endif
  12
  13 #include <linux/irqflags.h>
  14
  15 #ifndef xchg
  16
  17 /*
  18  * This function doesn't exist, so you'll get a linker error if
  19  * something tries to do an invalidly-sized xchg().
  20  */
  21 extern void __xchg_called_with_bad_pointer(void);
  22
  23 static inline
  24 unsigned long __xchg(unsigned long x, volatile void *ptr, int size)
  25 {
  26         unsigned long ret, flags;
  27
  28         switch (size) {
  29         case 1:
  30 #ifdef __xchg_u8
  31                 return __xchg_u8(x, ptr);
  32 #else
  33                 local_irq_save(flags);
  34                 ret = *(volatile u8 *)ptr;
  35                 *(volatile u8 *)ptr = x;
  36                 local_irq_restore(flags);
  37                 return ret;
  38 #endif /* __xchg_u8 */
  39
  40         case 2:
  41 #ifdef __xchg_u16
  42                 return __xchg_u16(x, ptr);
  43 #else
  44                 local_irq_save(flags);
  45                 ret = *(volatile u16 *)ptr;
  46                 *(volatile u16 *)ptr = x;
  47                 local_irq_restore(flags);
  48                 return ret;
  49 #endif /* __xchg_u16 */
  50
  51         case 4:
  52 #ifdef __xchg_u32
  53                 return __xchg_u32(x, ptr);
  54 #else
  55                 local_irq_save(flags);
  56                 ret = *(volatile u32 *)ptr;
  57                 *(volatile u32 *)ptr = x;
  58                 local_irq_restore(flags);
  59                 return ret;
  60 #endif /* __xchg_u32 */
  61
  62 #ifdef CONFIG_64BIT
  63         case 8:
  64 #ifdef __xchg_u64
  65                 return __xchg_u64(x, ptr);
  66 #else
  67                 local_irq_save(flags);
  68                 ret = *(volatile u64 *)ptr;
  69                 *(volatile u64 *)ptr = x;
  70                 local_irq_restore(flags);
  71                 return ret;
  72 #endif /* __xchg_u64 */
  73 #endif /* CONFIG_64BIT */
  74
  75         default:
  76                 __xchg_called_with_bad_pointer();
  77                 return x;
  78         }
  79 }
  80
  81 #define xchg(ptr, x) \
  82         ((__typeof__(*(ptr))) __xchg((unsigned long)(x), (ptr), sizeof(*(ptr))))
  83
  84 #endif /* xchg */
  85
  86 /*
  87  * Atomic compare and exchange.
  88  *
  89  * Do not define __HAVE_ARCH_CMPXCHG because we want to use it to check whether
  90  * a cmpxchg primitive faster than repeated local irq save/restore exists.
  91  */
  92 #include <asm-generic/cmpxchg-local.h>
  93
  94 #define cmpxchg(ptr, o, n)      cmpxchg_local((ptr), (o), (n))
  95 #define cmpxchg64(ptr, o, n)    cmpxchg64_local((ptr), (o), (n))
  96
  97 #endif /* __ASM_GENERIC_CMPXCHG_H */