include/asm-generic/cmpxchg.h

0001 /* SPDX-License-Identifier: GPL-2.0 */
0002 /*
0003  * Generic UP xchg and cmpxchg using interrupt disablement.  Does not
0004  * support SMP.
0005  */
0006
0007 #ifndef __ASM_GENERIC_CMPXCHG_H
0008 #define __ASM_GENERIC_CMPXCHG_H
0009
0010 #ifdef CONFIG_SMP
0011 #error "Cannot use generic cmpxchg on SMP"
0012 #endif
0013
0014 #include <linux/types.h>
0015 #include <linux/irqflags.h>
0016
0017 /*
0018  * This function doesn't exist, so you'll get a linker error if
0019  * something tries to do an invalidly-sized xchg().
0020  */
0021 extern void __generic_xchg_called_with_bad_pointer(void);
0022
0023 static inline
0024 unsigned long __generic_xchg(unsigned long x, volatile void *ptr, int size)
0025 {
0026     unsigned long ret, flags;
0027
0028     switch (size) {
0029     case 1:
0030 #ifdef __xchg_u8
0031         return __xchg_u8(x, ptr);
0032 #else
0033         local_irq_save(flags);
0034         ret = *(volatile u8 *)ptr;
0035         *(volatile u8 *)ptr = x;
0036         local_irq_restore(flags);
0037         return ret;
0038 #endif /* __xchg_u8 */
0039
0040     case 2:
0041 #ifdef __xchg_u16
0042         return __xchg_u16(x, ptr);
0043 #else
0044         local_irq_save(flags);
0045         ret = *(volatile u16 *)ptr;
0046         *(volatile u16 *)ptr = x;
0047         local_irq_restore(flags);
0048         return ret;
0049 #endif /* __xchg_u16 */
0050
0051     case 4:
0052 #ifdef __xchg_u32
0053         return __xchg_u32(x, ptr);
0054 #else
0055         local_irq_save(flags);
0056         ret = *(volatile u32 *)ptr;
0057         *(volatile u32 *)ptr = x;
0058         local_irq_restore(flags);
0059         return ret;
0060 #endif /* __xchg_u32 */
0061
0062 #ifdef CONFIG_64BIT
0063     case 8:
0064 #ifdef __xchg_u64
0065         return __xchg_u64(x, ptr);
0066 #else
0067         local_irq_save(flags);
0068         ret = *(volatile u64 *)ptr;
0069         *(volatile u64 *)ptr = x;
0070         local_irq_restore(flags);
0071         return ret;
0072 #endif /* __xchg_u64 */
0073 #endif /* CONFIG_64BIT */
0074
0075     default:
0076         __generic_xchg_called_with_bad_pointer();
0077         return x;
0078     }
0079 }
0080
0081 #define generic_xchg(ptr, x) ({                         \
0082     ((__typeof__(*(ptr)))                           \
0083         __generic_xchg((unsigned long)(x), (ptr), sizeof(*(ptr)))); \
0084 })
0085
0086 /*
0087  * Atomic compare and exchange.
0088  */
0089 #include <asm-generic/cmpxchg-local.h>
0090
0091 #define generic_cmpxchg_local(ptr, o, n) ({                 \
0092     ((__typeof__(*(ptr)))__generic_cmpxchg_local((ptr), (unsigned long)(o), \
0093             (unsigned long)(n), sizeof(*(ptr))));           \
0094 })
0095
0096 #define generic_cmpxchg64_local(ptr, o, n) \
0097     __generic_cmpxchg64_local((ptr), (o), (n))
0098
0099
0100 #ifndef arch_xchg
0101 #define arch_xchg       generic_xchg
0102 #endif
0103
0104 #ifndef arch_cmpxchg_local
0105 #define arch_cmpxchg_local  generic_cmpxchg_local
0106 #endif
0107
0108 #ifndef arch_cmpxchg64_local
0109 #define arch_cmpxchg64_local    generic_cmpxchg64_local
0110 #endif
0111
0112 #define arch_cmpxchg        arch_cmpxchg_local
0113 #define arch_cmpxchg64      arch_cmpxchg64_local
0114
0115 #endif /* __ASM_GENERIC_CMPXCHG_H */