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 | struct optimistic_spin_node { |
10 | struct optimistic_spin_node *next, *prev; |
11 | int locked; /* 1 if lock acquired */ |
12 | int cpu; /* encoded CPU # + 1 value */ |
13 | }; |
14 | |
15 | struct optimistic_spin_queue { |
16 | /* |
17 | * Stores an encoded value of the CPU # of the tail node in the queue. |
18 | * If the queue is empty, then it's set to OSQ_UNLOCKED_VAL. |
19 | */ |
20 | atomic_t tail; |
21 | }; |
22 | |
23 | #define OSQ_UNLOCKED_VAL (0) |
24 | |
25 | /* Init macro and function. */ |
26 | #define OSQ_LOCK_UNLOCKED { ATOMIC_INIT(OSQ_UNLOCKED_VAL) } |
27 | |
28 | static inline void osq_lock_init(struct optimistic_spin_queue *lock) |
29 | { |
30 | atomic_set(v: &lock->tail, OSQ_UNLOCKED_VAL); |
31 | } |
32 | |
33 | extern bool osq_lock(struct optimistic_spin_queue *lock); |
34 | extern void osq_unlock(struct optimistic_spin_queue *lock); |
35 | |
36 | static inline bool osq_is_locked(struct optimistic_spin_queue *lock) |
37 | { |
38 | return atomic_read(v: &lock->tail) != OSQ_UNLOCKED_VAL; |
39 | } |
40 | |
41 | #endif |
42 | |