pcmsg(D3)pcmsg(D3)NAMEpcmsg - test whether a message is a priority control message
SYNOPSIS
#include <sys/types.h>
#include <sys/stream.h>
#include <sys/ddi.h>
int pcmsg(uchar_t type);
Arguments
type The type of message to be tested.
DESCRIPTION
The pcmsg function tests the type of message to determine if it is a
priority control message (also known as a high priority message).
Return Values
pcmsg returns 1 if the message is a priority control message and 0 if the
message is any other type.
USAGE
The db_type field of the datab(D4) structure contains the message type.
This field may be accessed through the message block using mp->b_datap-
>db_type.
Level
Base or Interrupt.
Synchronization Constraints
Does not sleep.
Driver-defined basic locks, read/write locks, and sleep locks may be held
across calls to this function.
Examples
The service routine processes messages on the queue. If the message is a
high priority message, or if it is a normal message and the stream is not
flow-controlled, the message is processed and passed along in the stream.
Otherwise, the message is placed back on the head of the queue and the
service routine returns.
1 xxxsrv(q)
2 queue_t *q;
3 {
4 mblk_t *mp;
5 while ((mp = getq(q)) != NULL) {
6 if (pcmsg(mp->b_datap->db_type) || canputnext(q->g_next)) {
7 /* process message */
8 putnext(q, mp);
9 } else {
10 putbq(q, mp);
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pcmsg(D3)pcmsg(D3)
11 return;
12 }
13 }
14 }
REFERENCESallocb(D3), datab(D4), msgb(D4), messages(D5)
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