1 | /* SPDX-License-Identifier: GPL-2.0 */ |
2 | #ifndef __LINUX_BIT_SPINLOCK_H |
3 | #define __LINUX_BIT_SPINLOCK_H |
4 | |
5 | #include <linux/kernel.h> |
6 | #include <linux/preempt.h> |
7 | #include <linux/atomic.h> |
8 | #include <linux/bug.h> |
9 | |
10 | /* |
11 | * bit-based spin_lock() |
12 | * |
13 | * Don't use this unless you really need to: spin_lock() and spin_unlock() |
14 | * are significantly faster. |
15 | */ |
16 | static inline void bit_spin_lock(int bitnum, unsigned long *addr) |
17 | { |
18 | /* |
19 | * Assuming the lock is uncontended, this never enters |
20 | * the body of the outer loop. If it is contended, then |
21 | * within the inner loop a non-atomic test is used to |
22 | * busywait with less bus contention for a good time to |
23 | * attempt to acquire the lock bit. |
24 | */ |
25 | preempt_disable(); |
26 | #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) |
27 | while (unlikely(test_and_set_bit_lock(bitnum, addr))) { |
28 | preempt_enable(); |
29 | do { |
30 | cpu_relax(); |
31 | } while (test_bit(bitnum, addr)); |
32 | preempt_disable(); |
33 | } |
34 | #endif |
35 | __acquire(bitlock); |
36 | } |
37 | |
38 | /* |
39 | * Return true if it was acquired |
40 | */ |
41 | static inline int bit_spin_trylock(int bitnum, unsigned long *addr) |
42 | { |
43 | preempt_disable(); |
44 | #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) |
45 | if (unlikely(test_and_set_bit_lock(bitnum, addr))) { |
46 | preempt_enable(); |
47 | return 0; |
48 | } |
49 | #endif |
50 | __acquire(bitlock); |
51 | return 1; |
52 | } |
53 | |
54 | /* |
55 | * bit-based spin_unlock() |
56 | */ |
57 | static inline void bit_spin_unlock(int bitnum, unsigned long *addr) |
58 | { |
59 | #ifdef CONFIG_DEBUG_SPINLOCK |
60 | BUG_ON(!test_bit(bitnum, addr)); |
61 | #endif |
62 | #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) |
63 | clear_bit_unlock(nr: bitnum, addr); |
64 | #endif |
65 | preempt_enable(); |
66 | __release(bitlock); |
67 | } |
68 | |
69 | /* |
70 | * bit-based spin_unlock() |
71 | * non-atomic version, which can be used eg. if the bit lock itself is |
72 | * protecting the rest of the flags in the word. |
73 | */ |
74 | static inline void __bit_spin_unlock(int bitnum, unsigned long *addr) |
75 | { |
76 | #ifdef CONFIG_DEBUG_SPINLOCK |
77 | BUG_ON(!test_bit(bitnum, addr)); |
78 | #endif |
79 | #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) |
80 | __clear_bit_unlock(nr: bitnum, addr); |
81 | #endif |
82 | preempt_enable(); |
83 | __release(bitlock); |
84 | } |
85 | |
86 | /* |
87 | * Return true if the lock is held. |
88 | */ |
89 | static inline int bit_spin_is_locked(int bitnum, unsigned long *addr) |
90 | { |
91 | #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) |
92 | return test_bit(bitnum, addr); |
93 | #elif defined CONFIG_PREEMPT_COUNT |
94 | return preempt_count(); |
95 | #else |
96 | return 1; |
97 | #endif |
98 | } |
99 | |
100 | #endif /* __LINUX_BIT_SPINLOCK_H */ |
101 | |
102 | |