include/linux/osq_lock.h

   1 #ifndef __LINUX_OSQ_LOCK_H
   2 #define __LINUX_OSQ_LOCK_H
   3
   4 /*
   5  * An MCS like lock especially tailored for optimistic spinning for sleeping
   6  * lock implementations (mutex, rwsem, etc).
   7  */
   8
   9 #define OSQ_UNLOCKED_VAL (0)
  10
  11 struct optimistic_spin_queue {
  12         /*
  13          * Stores an encoded value of the CPU # of the tail node in the queue.
  14          * If the queue is empty, then it's set to OSQ_UNLOCKED_VAL.
  15          */
  16         atomic_t tail;
  17 };
  18
  19 /* Init macro and function. */
  20 #define OSQ_LOCK_UNLOCKED { ATOMIC_INIT(OSQ_UNLOCKED_VAL) }
  21
  22 static inline void osq_lock_init(struct optimistic_spin_queue *lock)
  23 {
  24         atomic_set(&lock->tail, OSQ_UNLOCKED_VAL);
  25 }
  26
  27 #endif