osq_lock.h 1.0 KB

1234567891011121314151617181920212223242526272829303132333435363738394041
  1. /* SPDX-License-Identifier: GPL-2.0 */
  2. #ifndef __LINUX_OSQ_LOCK_H
  3. #define __LINUX_OSQ_LOCK_H
  4. /*
  5. * An MCS like lock especially tailored for optimistic spinning for sleeping
  6. * lock implementations (mutex, rwsem, etc).
  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. };
  13. struct optimistic_spin_queue {
  14. /*
  15. * Stores an encoded value of the CPU # of the tail node in the queue.
  16. * If the queue is empty, then it's set to OSQ_UNLOCKED_VAL.
  17. */
  18. atomic_t tail;
  19. };
  20. #define OSQ_UNLOCKED_VAL (0)
  21. /* Init macro and function. */
  22. #define OSQ_LOCK_UNLOCKED { ATOMIC_INIT(OSQ_UNLOCKED_VAL) }
  23. static inline void osq_lock_init(struct optimistic_spin_queue *lock)
  24. {
  25. atomic_set(&lock->tail, OSQ_UNLOCKED_VAL);
  26. }
  27. extern bool osq_lock(struct optimistic_spin_queue *lock);
  28. extern void osq_unlock(struct optimistic_spin_queue *lock);
  29. static inline bool osq_is_locked(struct optimistic_spin_queue *lock)
  30. {
  31. return atomic_read(&lock->tail) != OSQ_UNLOCKED_VAL;
  32. }
  33. #endif