blob: 6b20af0bbb79d2037cfb3c5aa69d6b3cac2f2e59 [file] [log] [blame]
Ingo Molnarfb1c8f92005-09-10 00:25:56 -07001#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 (test_and_set_bit(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 (test_and_set_bit(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#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
54 BUG_ON(!test_bit(bitnum, addr));
55 smp_mb__before_clear_bit();
56 clear_bit(bitnum, addr);
57#endif
58 preempt_enable();
59 __release(bitlock);
60}
61
62/*
63 * Return true if the lock is held.
64 */
65static inline int bit_spin_is_locked(int bitnum, unsigned long *addr)
66{
67#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
68 return test_bit(bitnum, addr);
69#elif defined CONFIG_PREEMPT
70 return preempt_count();
71#else
72 return 1;
73#endif
74}
75
76#endif /* __LINUX_BIT_SPINLOCK_H */
77