1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ASM_GENERIC_BITOPS_LOCK_H_
3 #define _ASM_GENERIC_BITOPS_LOCK_H_
4
5 #include <linux/atomic.h>
6 #include <linux/compiler.h>
7 #include <asm/barrier.h>
8
9 /**
10 * test_and_set_bit_lock - Set a bit and return its old value, for lock
11 * @nr: Bit to set
12 * @addr: Address to count from
13 *
14 * This operation is atomic and provides acquire barrier semantics if
15 * the returned value is 0.
16 * It can be used to implement bit locks.
17 */
test_and_set_bit_lock(unsigned int nr,volatile unsigned long * p)18 static inline int test_and_set_bit_lock(unsigned int nr,
19 volatile unsigned long *p)
20 {
21 long old;
22 unsigned long mask = BIT_MASK(nr);
23
24 p += BIT_WORD(nr);
25 if (READ_ONCE(*p) & mask)
26 return 1;
27
28 old = atomic_long_fetch_or_acquire(mask, (atomic_long_t *)p);
29 return !!(old & mask);
30 }
31
32
33 /**
34 * clear_bit_unlock - Clear a bit in memory, for unlock
35 * @nr: the bit to set
36 * @addr: the address to start counting from
37 *
38 * This operation is atomic and provides release barrier semantics.
39 */
clear_bit_unlock(unsigned int nr,volatile unsigned long * p)40 static inline void clear_bit_unlock(unsigned int nr, volatile unsigned long *p)
41 {
42 p += BIT_WORD(nr);
43 atomic_long_fetch_andnot_release(BIT_MASK(nr), (atomic_long_t *)p);
44 }
45
46 /**
47 * __clear_bit_unlock - Clear a bit in memory, for unlock
48 * @nr: the bit to set
49 * @addr: the address to start counting from
50 *
51 * A weaker form of clear_bit_unlock() as used by __bit_lock_unlock(). If all
52 * the bits in the word are protected by this lock some archs can use weaker
53 * ops to safely unlock.
54 *
55 * See for example x86's implementation.
56 */
__clear_bit_unlock(unsigned int nr,volatile unsigned long * p)57 static inline void __clear_bit_unlock(unsigned int nr,
58 volatile unsigned long *p)
59 {
60 unsigned long old;
61
62 p += BIT_WORD(nr);
63 old = READ_ONCE(*p);
64 old &= ~BIT_MASK(nr);
65 atomic_long_set_release((atomic_long_t *)p, old);
66 }
67
68 /**
69 * clear_bit_unlock_is_negative_byte - Clear a bit in memory and test if bottom
70 * byte is negative, for unlock.
71 * @nr: the bit to clear
72 * @addr: the address to start counting from
73 *
74 * This is a bit of a one-trick-pony for the filemap code, which clears
75 * PG_locked and tests PG_waiters,
76 */
77 #ifndef clear_bit_unlock_is_negative_byte
clear_bit_unlock_is_negative_byte(unsigned int nr,volatile unsigned long * p)78 static inline bool clear_bit_unlock_is_negative_byte(unsigned int nr,
79 volatile unsigned long *p)
80 {
81 long old;
82 unsigned long mask = BIT_MASK(nr);
83
84 p += BIT_WORD(nr);
85 old = atomic_long_fetch_andnot_release(mask, (atomic_long_t *)p);
86 return !!(old & BIT(7));
87 }
88 #define clear_bit_unlock_is_negative_byte clear_bit_unlock_is_negative_byte
89 #endif
90
91 #endif /* _ASM_GENERIC_BITOPS_LOCK_H_ */
92
