flushq(9F)

NAME

     flushq - remove messages from a queue

SYNOPSIS

     #include <sys/stream.h>

     void flushq(queue_t *q, int flag);

INTERFACE LEVEL

     Architecture independent level 1 (DDI/DKI).

PARAMETERS

     q     Pointer to the queue to be flushed.

     flag  Valid flag values are:

     FLUSHDATA
           Flush only data messages (types M_DATA M_DELAY M_PROTO
           and M_PCPROTO).

     FLUSHALL
           Flush all messages.

DESCRIPTION

     flushq() frees messages and their associated data structures
     by calling freemsg(9F). If the queue's count falls below the
     low water mark and the queue was blocking an  upstream  ser-
     vice  procedure,  the  nearest upstream service procedure is
     enabled.

CONTEXT

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

EXAMPLES

     Example 1: Using flushq()

     This example depicts the canonical flushing code for STREAMS
     modules. The module has a write service procedure and poten-
     tially has messages on the queue. If it receives an  M_FLUSH
     message,  and  if  the FLUSHR bit is on in the first byte of
     the message (line 10), then the read queue is flushed  (line
     11). If the FLUSHW bit is on (line 12), then the write queue
     is flushed (line 13). Then the message is  passed  along  to
     the next entity in the stream (line 14). See the example for
     qreply(9F) for the canonical flushing code for drivers.

           1  /*
           2   * Module write-side put procedure.
           3   */
           4  xxxwput(q, mp)
           5      queue_t *q;
           6      mblk_t *mp;
           7  {
           8   switch(mp->b_datap->db_type) {
           9      case M_FLUSH:
          10        if (*mp->b_rptr & FLUSHR)
          11             flushq(RD(q), FLUSHALL);
          12        if (*mp->b_rptr & FLUSHW)
          13             flushq(q, FLUSHALL);
          14        putnext(q, mp);
          15        break;
                    . . .
          16   }
          17  }

SEE ALSO

     flushband(9F), freemsg(9F), putq(9F), qreply(9F)

     Writing Device Drivers STREAMS Programming Guide