LXR linux/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 */
  23extern void __xchg_called_with_bad_pointer(void);
  24
  25static inline
  26unsigned 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 */
 110