flushq(9F) Kernel Functions for Drivers flushq(9F)NAMEflushq - 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
The flushq() function frees messages and their associated data strucā
tures by calling freemsg(9F). If the queue's count falls below the low
water mark and the queue was blocking an upstream service procedure,
the nearest upstream service procedure is enabled.
CONTEXT
The flushq() function can be called from user, interrupt, or kernel
context.
EXAMPLES
Example 1: Using flushq()
This example depicts the canonical flushing code for STREAMS modules.
The module has a write service procedure and potentially 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 ALSOflushband(9F), freemsg(9F), putq(9F), qreply(9F)
Writing Device Drivers STREAMS Programming Guide
SunOS 5.10 16 Jan 2006 flushq(9F)