1 | /* SPDX-License-Identifier: GPL-2.0 */ |
2 | #ifndef __LINUX_OSQ_LOCK_H |
3 | #define __LINUX_OSQ_LOCK_H |
4 | |
5 | /* |
6 | * An MCS like lock especially tailored for optimistic spinning for sleeping |
7 | * lock implementations (mutex, rwsem, etc). |
8 | */ |
9 | |
10 | struct optimistic_spin_queue { |
11 | /* |
12 | * Stores an encoded value of the CPU # of the tail node in the queue. |
13 | * If the queue is empty, then it's set to OSQ_UNLOCKED_VAL. |
14 | */ |
15 | atomic_t tail; |
16 | }; |
17 | |
18 | #define OSQ_UNLOCKED_VAL (0) |
19 | |
20 | /* Init macro and function. */ |
21 | #define OSQ_LOCK_UNLOCKED { ATOMIC_INIT(OSQ_UNLOCKED_VAL) } |
22 | |
23 | static inline void osq_lock_init(struct optimistic_spin_queue *lock) |
24 | { |
25 | atomic_set(v: &lock->tail, OSQ_UNLOCKED_VAL); |
26 | } |
27 | |
28 | extern bool osq_lock(struct optimistic_spin_queue *lock); |
29 | extern void osq_unlock(struct optimistic_spin_queue *lock); |
30 | |
31 | static inline bool osq_is_locked(struct optimistic_spin_queue *lock) |
32 | { |
33 | return atomic_read(v: &lock->tail) != OSQ_UNLOCKED_VAL; |
34 | } |
35 | |
36 | #endif |
37 | |