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/*
  18 * This function doesn't exist, so you'll get a linker error if
  19 * something tries to do an invalidly-sized xchg().
  20 */
  21extern void __generic_xchg_called_with_bad_pointer(void);
  22
  23static inline
  24unsigned long __generic_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                __generic_xchg_called_with_bad_pointer();
  77                return x;
  78        }
  79}
  80
  81#define generic_xchg(ptr, x) ({                                                 \
  82        ((__typeof__(*(ptr)))                                                   \
  83                __generic_xchg((unsigned long)(x), (ptr), sizeof(*(ptr))));     \
  84})
  85
  86/*
  87 * Atomic compare and exchange.
  88 */
  89#include <asm-generic/cmpxchg-local.h>
  90
  91#define generic_cmpxchg_local(ptr, o, n) ({                                     \
  92        ((__typeof__(*(ptr)))__generic_cmpxchg_local((ptr), (unsigned long)(o), \
  93                        (unsigned long)(n), sizeof(*(ptr))));                   \
  94})
  95
  96#define generic_cmpxchg64_local(ptr, o, n) \
  97        __generic_cmpxchg64_local((ptr), (o), (n))
  98
  99
 100#ifndef arch_xchg
 101#define arch_xchg               generic_xchg
 102#endif
 103
 104#ifndef arch_cmpxchg_local
 105#define arch_cmpxchg_local      generic_cmpxchg_local
 106#endif
 107
 108#ifndef arch_cmpxchg64_local
 109#define arch_cmpxchg64_local    generic_cmpxchg64_local
 110#endif
 111
 112#define arch_cmpxchg            arch_cmpxchg_local
 113#define arch_cmpxchg64          arch_cmpxchg64_local
 114
 115#endif /* __ASM_GENERIC_CMPXCHG_H */
 116