LXR linux/include/linux/osq

   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
  11struct 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
  22static inline void osq_lock_init(struct optimistic_spin_queue *lock)
  23{
  24        atomic_set(&lock->tail, OSQ_UNLOCKED_VAL);
  25}
  26
  27#endif
  28