include/asm-generic/cmpxchg.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * Generic UP xchg and cmpxchg using interrupt disablement.  Does not
   4  * support SMP.
   5  */
   6
   7 #ifndef __ASM_GENERIC_CMPXCHG_H
   8 #define __ASM_GENERIC_CMPXCHG_H
   9
  10 #ifdef CONFIG_SMP
  11 #error "Cannot use generic cmpxchg on SMP"
  12 #endif
  13
  14 #include <linux/types.h>
  15 #include <linux/irqflags.h>
  16
  17 #ifndef xchg
  18
  19 /*
  20  * This function doesn't exist, so you'll get a linker error if
  21  * something tries to do an invalidly-sized xchg().
  22  */
  23 extern void __xchg_called_with_bad_pointer(void);
  24
  25 static inline
  26 unsigned long __xchg(unsigned long x, volatile void *ptr, int size)
  27 {
  28         unsigned long ret, flags;
  29
  30         switch (size) {
  31         case 1:
  32 #ifdef __xchg_u8
  33                 return __xchg_u8(x, ptr);
  34 #else
  35                 local_irq_save(flags);
  36                 ret = *(volatile u8 *)ptr;
  37                 *(volatile u8 *)ptr = x;
  38                 local_irq_restore(flags);
  39                 return ret;
  40 #endif /* __xchg_u8 */
  41
  42         case 2:
  43 #ifdef __xchg_u16
  44                 return __xchg_u16(x, ptr);
  45 #else
  46                 local_irq_save(flags);
  47                 ret = *(volatile u16 *)ptr;
  48                 *(volatile u16 *)ptr = x;
  49                 local_irq_restore(flags);
  50                 return ret;
  51 #endif /* __xchg_u16 */
  52
  53         case 4:
  54 #ifdef __xchg_u32
  55                 return __xchg_u32(x, ptr);
  56 #else
  57                 local_irq_save(flags);
  58                 ret = *(volatile u32 *)ptr;
  59                 *(volatile u32 *)ptr = x;
  60                 local_irq_restore(flags);
  61                 return ret;
  62 #endif /* __xchg_u32 */
  63
  64 #ifdef CONFIG_64BIT
  65         case 8:
  66 #ifdef __xchg_u64
  67                 return __xchg_u64(x, ptr);
  68 #else
  69                 local_irq_save(flags);
  70                 ret = *(volatile u64 *)ptr;
  71                 *(volatile u64 *)ptr = x;
  72                 local_irq_restore(flags);
  73                 return ret;
  74 #endif /* __xchg_u64 */
  75 #endif /* CONFIG_64BIT */
  76
  77         default:
  78                 __xchg_called_with_bad_pointer();
  79                 return x;
  80         }
  81 }
  82
  83 #define xchg(ptr, x) ({                                                 \
  84         ((__typeof__(*(ptr)))                                           \
  85                 __xchg((unsigned long)(x), (ptr), sizeof(*(ptr))));     \
  86 })
  87
  88 #endif /* xchg */
  89
  90 /*
  91  * Atomic compare and exchange.
  92  */
  93 #include <asm-generic/cmpxchg-local.h>
  94
  95 #ifndef cmpxchg_local
  96 #define cmpxchg_local(ptr, o, n) ({                                            \
  97         ((__typeof__(*(ptr)))__cmpxchg_local_generic((ptr), (unsigned long)(o),\
  98                         (unsigned long)(n), sizeof(*(ptr))));                  \
  99 })
 100 #endif
 101
 102 #ifndef cmpxchg64_local
 103 #define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
 104 #endif
 105
 106 #define cmpxchg(ptr, o, n)      cmpxchg_local((ptr), (o), (n))
 107 #define cmpxchg64(ptr, o, n)    cmpxchg64_local((ptr), (o), (n))
 108
 109 #endif /* __ASM_GENERIC_CMPXCHG_H */