sched: mqueue wait list optimize

sched/mqueue/mq_msgqalloc.c

@@ -101,6 +101,9 @@ int nxmq_alloc_msgq(FAR struct mq_attr *attr,
 #ifndef CONFIG_DISABLE_MQUEUE_NOTIFICATION
       msgq->ntpid = INVALID_PROCESS_ID;
 #endif
+
+      dq_init(&msgq->waitfornotempty);
+      dq_init(&msgq->waitfornotfull);
     }
   else
     {

sched/mqueue/mq_rcvinternal.c

@@ -280,16 +280,12 @@ ssize_t nxmq_do_receive(FAR struct mqueue_inode_s *msgq,
   if (msgq->nwaitnotfull > 0)
     {
       /* Find the highest priority task that is waiting for
-       * this queue to be not-full in g_waitingformqnotfull list.
+       * this queue to be not-full in waitfornotfull list.
        * This must be performed in a critical section because
        * messages can be sent from interrupt handlers.
        */
 
-      for (btcb = (FAR struct tcb_s *)g_waitingformqnotfull.head;
-           btcb && btcb->waitobj != msgq;
-           btcb = btcb->flink)
-        {
-        }
+      btcb = (FAR struct tcb_s *)dq_peek(MQ_WNFLIST(msgq));
 
       /* If one was found, unblock it.  NOTE:  There is a race
        * condition here:  the queue might be full again by the

sched/mqueue/mq_sndinternal.c

@@ -389,17 +389,13 @@ int nxmq_do_send(FAR struct mqueue_inode_s *msgq,
   if (msgq->nwaitnotempty > 0)
     {
       /* Find the highest priority task that is waiting for
-       * this queue to be non-empty in g_waitingformqnotempty
+       * this queue to be non-empty in waitfornotempty
        * list. leave_critical_section() should give us sufficient
        * protection since interrupts should never cause a change
        * in this list
        */
 
-      for (btcb = (FAR struct tcb_s *)g_waitingformqnotempty.head;
-           btcb && btcb->waitobj != msgq;
-           btcb = btcb->flink)
-        {
-        }
+      btcb = (FAR struct tcb_s *)dq_peek(MQ_WNELIST(msgq));
 
       /* If one was found, unblock it */