rmvq(9F)

NAME

     rmvq - remove a message from a queue

SYNOPSIS

     #include <sys/stream.h>

     void rmvq(queue_t *q, mblk_t *mp);

INTERFACE LEVEL

     Architecture independent level 1 (DDI/DKI).

PARAMETERS

     q     Queue containing the message to be removed.

     mp    Message to remove.

DESCRIPTION

     rmvq() removes a message from a  queue.  A  message  can  be
     removed  from  anywhere  on  a queue. To prevent modules and
     drivers from having to deal with the  internals  of  message
     linkage on a queue, either rmvq() or getq(9F) should be used
     to remove a message from a queue.

CONTEXT

     rmvq() can be called from user or interrupt context.

EXAMPLES

     This code fragment illustrates how one may flush one type of
     message  from a queue. In this case, only M_PROTO T_DATA_IND
     messages are flushed. For each message on the queue,  if  it
     is an M_PROTO message (line 8) of type T_DATA_IND (line 10),
     save a pointer to the next message  (line  11),  remove  the
     T_DATA_IND message (line 12) and free it (line 13). Continue
     with the next message in the list (line 19).

      1  mblk_t *mp, *nmp;
      2  queue_t *q;
      3  union T_primitives *tp;
      4
      5   /* Insert code here to protect queue and message block */
      6   mp = q->q_first;
      7   while (mp) {
      8        if (mp->b_datap->db_type == M_PROTO) {
      9             tp = (union T_primitives *)mp->b_rptr;
     10             if (tp->type == T_DATA_IND) {
     11                  nmp = mp->b_next;
     12                  rmvq(q, mp);
     13                  freemsg(mp);
     14                  mp = nmp;
     15             } else {
     16                  mp = mp->b_next;
     17             }
     18        } else {
     19             mp = mp->b_next;
     20        }
     21   }
     22   /* End of region that must be protected */

     When using rmvq(), you must ensure that the  queue  and  the
     message  block is not modified by another thread at the same
     time. You can achieve this either by using STREAMS functions
     or by implementing your own locking.

SEE ALSO

     freemsg(9F), getq(9F), insq(9F)

     Writing Device Drivers

     STREAMS Programming Guide

WARNINGS

     Make sure that the message mp is linked onto q  to  avoid  a
     possible system panic.