1 /* SPDX-License-Identifier: GPL-2.0 */ <<
2 #ifndef __LINUX_OSQ_LOCK_H 1 #ifndef __LINUX_OSQ_LOCK_H
3 #define __LINUX_OSQ_LOCK_H 2 #define __LINUX_OSQ_LOCK_H
4 3
5 /* 4 /*
6 * An MCS like lock especially tailored for op 5 * An MCS like lock especially tailored for optimistic spinning for sleeping
7 * lock implementations (mutex, rwsem, etc). 6 * lock implementations (mutex, rwsem, etc).
8 */ 7 */
>> 8 struct optimistic_spin_node {
>> 9 struct optimistic_spin_node *next, *prev;
>> 10 int locked; /* 1 if lock acquired */
>> 11 int cpu; /* encoded CPU # + 1 value */
>> 12 };
9 13
10 struct optimistic_spin_queue { 14 struct optimistic_spin_queue {
11 /* 15 /*
12 * Stores an encoded value of the CPU 16 * Stores an encoded value of the CPU # of the tail node in the queue.
13 * If the queue is empty, then it's se 17 * If the queue is empty, then it's set to OSQ_UNLOCKED_VAL.
14 */ 18 */
15 atomic_t tail; 19 atomic_t tail;
16 }; 20 };
17 21
18 #define OSQ_UNLOCKED_VAL (0) 22 #define OSQ_UNLOCKED_VAL (0)
19 23
20 /* Init macro and function. */ 24 /* Init macro and function. */
21 #define OSQ_LOCK_UNLOCKED { ATOMIC_INIT(OSQ_UN 25 #define OSQ_LOCK_UNLOCKED { ATOMIC_INIT(OSQ_UNLOCKED_VAL) }
22 26
23 static inline void osq_lock_init(struct optimi 27 static inline void osq_lock_init(struct optimistic_spin_queue *lock)
24 { 28 {
25 atomic_set(&lock->tail, OSQ_UNLOCKED_V 29 atomic_set(&lock->tail, OSQ_UNLOCKED_VAL);
26 } 30 }
27 31
28 extern bool osq_lock(struct optimistic_spin_qu 32 extern bool osq_lock(struct optimistic_spin_queue *lock);
29 extern void osq_unlock(struct optimistic_spin_ 33 extern void osq_unlock(struct optimistic_spin_queue *lock);
30 34
31 static inline bool osq_is_locked(struct optimi 35 static inline bool osq_is_locked(struct optimistic_spin_queue *lock)
32 { 36 {
33 return atomic_read(&lock->tail) != OSQ 37 return atomic_read(&lock->tail) != OSQ_UNLOCKED_VAL;
34 } 38 }
35 39
36 #endif 40 #endif
37 41
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