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