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