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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) | |
b8dc93cb | 21 | while (unlikely(test_and_set_bit_lock(bitnum, addr))) { |
fb1c8f93 IM |
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) | |
b8dc93cb | 39 | if (unlikely(test_and_set_bit_lock(bitnum, addr))) { |
fb1c8f93 IM |
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 | { | |
b8dc93cb NP |
53 | #ifdef CONFIG_DEBUG_SPINLOCK |
54 | BUG_ON(!test_bit(bitnum, addr)); | |
55 | #endif | |
fb1c8f93 | 56 | #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) |
b8dc93cb NP |
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 | */ | |
68 | static inline void __bit_spin_unlock(int bitnum, unsigned long *addr) | |
69 | { | |
70 | #ifdef CONFIG_DEBUG_SPINLOCK | |
fb1c8f93 | 71 | BUG_ON(!test_bit(bitnum, addr)); |
b8dc93cb NP |
72 | #endif |
73 | #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) | |
74 | __clear_bit_unlock(bitnum, addr); | |
fb1c8f93 IM |
75 | #endif |
76 | preempt_enable(); | |
77 | __release(bitlock); | |
78 | } | |
79 | ||
80 | /* | |
81 | * Return true if the lock is held. | |
82 | */ | |
83 | static 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 |