1 /* SPDX-License-Identifier: GPL-2.0-only */
2 
3 #ifndef __ASM_GENERIC_BITOPS_GENERIC_NON_ATOMIC_H
4 #define __ASM_GENERIC_BITOPS_GENERIC_NON_ATOMIC_H
5 
6 #include <linux/bits.h>
7 
8 #ifndef _LINUX_BITOPS_H
9 #error only <linux/bitops.h> can be included directly
10 #endif
11 
12 /*
13  * Generic definitions for bit operations, should not be used in regular code
14  * directly.
15  */
16 
17 /**
18  * generic___set_bit - Set a bit in memory
19  * @nr: the bit to set
20  * @addr: the address to start counting from
21  *
22  * Unlike set_bit(), this function is non-atomic and may be reordered.
23  * If it's called on the same region of memory simultaneously, the effect
24  * may be that only one operation succeeds.
25  */
26 static __always_inline void
27 generic___set_bit(unsigned long nr, volatile unsigned long *addr)
28 {
29 	unsigned long mask = BIT_MASK(nr);
30 	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
31 
32 	*p  |= mask;
33 }
34 
35 static __always_inline void
36 generic___clear_bit(unsigned long nr, volatile unsigned long *addr)
37 {
38 	unsigned long mask = BIT_MASK(nr);
39 	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
40 
41 	*p &= ~mask;
42 }
43 
44 /**
45  * generic___change_bit - Toggle a bit in memory
46  * @nr: the bit to change
47  * @addr: the address to start counting from
48  *
49  * Unlike change_bit(), this function is non-atomic and may be reordered.
50  * If it's called on the same region of memory simultaneously, the effect
51  * may be that only one operation succeeds.
52  */
53 static __always_inline void
54 generic___change_bit(unsigned long nr, volatile unsigned long *addr)
55 {
56 	unsigned long mask = BIT_MASK(nr);
57 	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
58 
59 	*p ^= mask;
60 }
61 
62 /**
63  * generic___test_and_set_bit - Set a bit and return its old value
64  * @nr: Bit to set
65  * @addr: Address to count from
66  *
67  * This operation is non-atomic and can be reordered.
68  * If two examples of this operation race, one can appear to succeed
69  * but actually fail.  You must protect multiple accesses with a lock.
70  */
71 static __always_inline bool
72 generic___test_and_set_bit(unsigned long nr, volatile unsigned long *addr)
73 {
74 	unsigned long mask = BIT_MASK(nr);
75 	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
76 	unsigned long old = *p;
77 
78 	*p = old | mask;
79 	return (old & mask) != 0;
80 }
81 
82 /**
83  * generic___test_and_clear_bit - Clear a bit and return its old value
84  * @nr: Bit to clear
85  * @addr: Address to count from
86  *
87  * This operation is non-atomic and can be reordered.
88  * If two examples of this operation race, one can appear to succeed
89  * but actually fail.  You must protect multiple accesses with a lock.
90  */
91 static __always_inline bool
92 generic___test_and_clear_bit(unsigned long nr, volatile unsigned long *addr)
93 {
94 	unsigned long mask = BIT_MASK(nr);
95 	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
96 	unsigned long old = *p;
97 
98 	*p = old & ~mask;
99 	return (old & mask) != 0;
100 }
101 
102 /* WARNING: non atomic and it can be reordered! */
103 static __always_inline bool
104 generic___test_and_change_bit(unsigned long nr, volatile unsigned long *addr)
105 {
106 	unsigned long mask = BIT_MASK(nr);
107 	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
108 	unsigned long old = *p;
109 
110 	*p = old ^ mask;
111 	return (old & mask) != 0;
112 }
113 
114 /**
115  * generic_test_bit - Determine whether a bit is set
116  * @nr: bit number to test
117  * @addr: Address to start counting from
118  */
119 static __always_inline bool
120 generic_test_bit(unsigned long nr, const volatile unsigned long *addr)
121 {
122 	/*
123 	 * Unlike the bitops with the '__' prefix above, this one *is* atomic,
124 	 * so `volatile` must always stay here with no cast-aways. See
125 	 * `Documentation/atomic_bitops.txt` for the details.
126 	 */
127 	return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
128 }
129 
130 /*
131  * const_*() definitions provide good compile-time optimizations when
132  * the passed arguments can be resolved at compile time.
133  */
134 #define const___set_bit			generic___set_bit
135 #define const___clear_bit		generic___clear_bit
136 #define const___change_bit		generic___change_bit
137 #define const___test_and_set_bit	generic___test_and_set_bit
138 #define const___test_and_clear_bit	generic___test_and_clear_bit
139 #define const___test_and_change_bit	generic___test_and_change_bit
140 
141 /**
142  * const_test_bit - Determine whether a bit is set
143  * @nr: bit number to test
144  * @addr: Address to start counting from
145  *
146  * A version of generic_test_bit() which discards the `volatile` qualifier to
147  * allow a compiler to optimize code harder. Non-atomic and to be called only
148  * for testing compile-time constants, e.g. by the corresponding macros, not
149  * directly from "regular" code.
150  */
151 static __always_inline bool
152 const_test_bit(unsigned long nr, const volatile unsigned long *addr)
153 {
154 	const unsigned long *p = (const unsigned long *)addr + BIT_WORD(nr);
155 	unsigned long mask = BIT_MASK(nr);
156 	unsigned long val = *p;
157 
158 	return !!(val & mask);
159 }
160 
161 #endif /* __ASM_GENERIC_BITOPS_GENERIC_NON_ATOMIC_H */
162