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 */
bit_spin_lock(int bitnum,unsigned long * addr)15 static 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 */
bit_spin_trylock(int bitnum,unsigned long * addr)40 static 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 */
bit_spin_unlock(int bitnum,unsigned long * addr)56 static 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 */
__bit_spin_unlock(int bitnum,unsigned long * addr)73 static 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 */
bit_spin_is_locked(int bitnum,unsigned long * addr)88 static 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