Manual Pages for UNIX Operating System command usage for man rmvq

Kernel Functions for Drivers                             rmvq(9F)



NAME
     rmvq - remove a message from a queue

SYNOPSIS
     #include 



     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
     The rmvq() function removes a message from a queue.  A  mes-
     sage  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
     The rmvq() function can be called from user,  interrupt,  or
     kernel 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;



SunOS 5.11          Last change: 16 Jan 2006                    1






Kernel Functions for Drivers                             rmvq(9F)



       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.
























SunOS 5.11          Last change: 16 Jan 2006                    2