1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __LINUX_BIT_SPINLOCK_H
3#define __LINUX_BIT_SPINLOCK_H
4
5#include <linux/kernel.h>
6#include <linux/preempt.h>
7#include <linux/atomic.h>
8#include <linux/bug.h>
9
10/*
11 *  bit-based spin_lock()
12 *
13 * Don't use this unless you really need to: spin_lock() and spin_unlock()
14 * are significantly faster.
15 */
16static inline void bit_spin_lock(int bitnum, unsigned long *addr)
17{
18	/*
19	 * Assuming the lock is uncontended, this never enters
20	 * the body of the outer loop. If it is contended, then
21	 * within the inner loop a non-atomic test is used to
22	 * busywait with less bus contention for a good time to
23	 * attempt to acquire the lock bit.
24	 */
25	preempt_disable();
26#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
27	while (unlikely(test_and_set_bit_lock(bitnum, addr))) {
28		preempt_enable();
29		do {
30			cpu_relax();
31		} while (test_bit(bitnum, addr));
32		preempt_disable();
33	}
34#endif
35	__acquire(bitlock);
36}
37
38/*
39 * Return true if it was acquired
40 */
41static inline int bit_spin_trylock(int bitnum, unsigned long *addr)
42{
43	preempt_disable();
44#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
45	if (unlikely(test_and_set_bit_lock(bitnum, addr))) {
46		preempt_enable();
47		return 0;
48	}
49#endif
50	__acquire(bitlock);
51	return 1;
52}
53
54/*
55 *  bit-based spin_unlock()
56 */
57static inline void bit_spin_unlock(int bitnum, unsigned long *addr)
58{
59#ifdef CONFIG_DEBUG_SPINLOCK
60	BUG_ON(!test_bit(bitnum, addr));
61#endif
62#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
63	clear_bit_unlock(bitnum, addr);
64#endif
65	preempt_enable();
66	__release(bitlock);
67}
68
69/*
70 *  bit-based spin_unlock()
71 *  non-atomic version, which can be used eg. if the bit lock itself is
72 *  protecting the rest of the flags in the word.
73 */
74static inline void __bit_spin_unlock(int bitnum, unsigned long *addr)
75{
76#ifdef CONFIG_DEBUG_SPINLOCK
77	BUG_ON(!test_bit(bitnum, addr));
78#endif
79#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
80	__clear_bit_unlock(bitnum, addr);
81#endif
82	preempt_enable();
83	__release(bitlock);
84}
85
86/*
87 * Return true if the lock is held.
88 */
89static inline int bit_spin_is_locked(int bitnum, unsigned long *addr)
90{
91#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
92	return test_bit(bitnum, addr);
93#elif defined CONFIG_PREEMPT_COUNT
94	return preempt_count();
95#else
96	return 1;
97#endif
98}
99
100#endif /* __LINUX_BIT_SPINLOCK_H */
101
102