Linux Audio

Check our new training course

Embedded Linux Audio

Check our new training course
with Creative Commons CC-BY-SA
lecture materials

Bootlin logo

Elixir Cross Referencer

Open Menu / include / asm-generic / bitops / lock.h
Loading...
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_GENERIC_BITOPS_LOCK_H_
#define _ASM_GENERIC_BITOPS_LOCK_H_

#include <linux/atomic.h>
#include <linux/compiler.h>
#include <asm/barrier.h>

/**
 * arch_test_and_set_bit_lock - Set a bit and return its old value, for lock
 * @nr: Bit to set
 * @addr: Address to count from
 *
 * This operation is atomic and provides acquire barrier semantics if
 * the returned value is 0.
 * It can be used to implement bit locks.
 */
static __always_inline int
arch_test_and_set_bit_lock(unsigned int nr, volatile unsigned long *p)
{
	long old;
	unsigned long mask = BIT_MASK(nr);

	p += BIT_WORD(nr);
	if (READ_ONCE(*p) & mask)
		return 1;

	old = raw_atomic_long_fetch_or_acquire(mask, (atomic_long_t *)p);
	return !!(old & mask);
}


/**
 * arch_clear_bit_unlock - Clear a bit in memory, for unlock
 * @nr: the bit to set
 * @addr: the address to start counting from
 *
 * This operation is atomic and provides release barrier semantics.
 */
static __always_inline void
arch_clear_bit_unlock(unsigned int nr, volatile unsigned long *p)
{
	p += BIT_WORD(nr);
	raw_atomic_long_fetch_andnot_release(BIT_MASK(nr), (atomic_long_t *)p);
}

/**
 * arch___clear_bit_unlock - Clear a bit in memory, for unlock
 * @nr: the bit to set
 * @addr: the address to start counting from
 *
 * A weaker form of clear_bit_unlock() as used by __bit_lock_unlock(). If all
 * the bits in the word are protected by this lock some archs can use weaker
 * ops to safely unlock.
 *
 * See for example x86's implementation.
 */
static inline void
arch___clear_bit_unlock(unsigned int nr, volatile unsigned long *p)
{
	unsigned long old;

	p += BIT_WORD(nr);
	old = READ_ONCE(*p);
	old &= ~BIT_MASK(nr);
	raw_atomic_long_set_release((atomic_long_t *)p, old);
}

/**
 * arch_clear_bit_unlock_is_negative_byte - Clear a bit in memory and test if bottom
 *                                          byte is negative, for unlock.
 * @nr: the bit to clear
 * @addr: the address to start counting from
 *
 * This is a bit of a one-trick-pony for the filemap code, which clears
 * PG_locked and tests PG_waiters,
 */
#ifndef arch_clear_bit_unlock_is_negative_byte
static inline bool arch_clear_bit_unlock_is_negative_byte(unsigned int nr,
							  volatile unsigned long *p)
{
	long old;
	unsigned long mask = BIT_MASK(nr);

	p += BIT_WORD(nr);
	old = raw_atomic_long_fetch_andnot_release(mask, (atomic_long_t *)p);
	return !!(old & BIT(7));
}
#define arch_clear_bit_unlock_is_negative_byte arch_clear_bit_unlock_is_negative_byte
#endif

#include <asm-generic/bitops/instrumented-lock.h>

#endif /* _ASM_GENERIC_BITOPS_LOCK_H_ */