1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _TOOLS_LINUX_ASM_X86_ATOMIC_H 3 #define _TOOLS_LINUX_ASM_X86_ATOMIC_H 4 5 #include <linux/compiler.h> 6 #include <linux/types.h> 7 #include "rmwcc.h" 8 9 #define LOCK_PREFIX "\n\tlock; " 10 11 #include <asm/cmpxchg.h> 12 13 /* 14 * Atomic operations that C can't guarantee us. Useful for 15 * resource counting etc.. 16 */ 17 18 #define ATOMIC_INIT(i) { (i) } 19 20 /** 21 * atomic_read - read atomic variable 22 * @v: pointer of type atomic_t 23 * 24 * Atomically reads the value of @v. 25 */ 26 static inline int atomic_read(const atomic_t *v) 27 { 28 return READ_ONCE((v)->counter); 29 } 30 31 /** 32 * atomic_set - set atomic variable 33 * @v: pointer of type atomic_t 34 * @i: required value 35 * 36 * Atomically sets the value of @v to @i. 37 */ 38 static inline void atomic_set(atomic_t *v, int i) 39 { 40 v->counter = i; 41 } 42 43 /** 44 * atomic_inc - increment atomic variable 45 * @v: pointer of type atomic_t 46 * 47 * Atomically increments @v by 1. 48 */ 49 static inline void atomic_inc(atomic_t *v) 50 { 51 asm volatile(LOCK_PREFIX "incl %0" 52 : "+m" (v->counter)); 53 } 54 55 /** 56 * atomic_dec_and_test - decrement and test 57 * @v: pointer of type atomic_t 58 * 59 * Atomically decrements @v by 1 and 60 * returns true if the result is 0, or false for all other 61 * cases. 62 */ 63 static inline int atomic_dec_and_test(atomic_t *v) 64 { 65 GEN_UNARY_RMWcc(LOCK_PREFIX "decl", v->counter, "%0", "e"); 66 } 67 68 static __always_inline int atomic_cmpxchg(atomic_t *v, int old, int new) 69 { 70 return cmpxchg(&v->counter, old, new); 71 } 72 73 #endif /* _TOOLS_LINUX_ASM_X86_ATOMIC_H */ 74