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fb1c8f93 IM |
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 | */ | |
10 | static 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 | */ | |
35 | static 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 | */ | |
51 | static 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 | */ | |
65 | static 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 |