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