Man page 9 : eventfd_ctx_remove_wait_queue

eventfd_ctx_remove_wait_queue - Read the current counter and removes wait queue.

int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *  ctx , wait_queue_t *  wait , __u64 *  cnt );

ctx
    [in] Pointer to eventfd context.

wait
    [in] Wait queue to be removed.

cnt
    [out] Pointer to the 64-bit counter value.

Returns 0 if successful, or the following error codes:

-EAGAIN : The operation would have blocked.

This is used to atomically remove a wait queue entry from the eventfd wait queue head, and read/reset the counter value.