flushq(9F)

NAME

flushq − remove messages from a queue

SYNOPSIS

#include <sys/stream.h>
void flushq(queue_t ∗q, int flag);

ARGUMENTS

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.

INTERFACE LEVEL

Architecture independent level 1 (DDI/DKI).

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 QWANTW is set, the nearest upstream service procedure is enabled.

CONTEXT

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

EXAMPLE

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 {
8switch(mp->b_datap->db_type) {
9   case M_FLUSH:
10if (∗mp->b_rptr & FLUSHR)
11flushq(RD(q), FLUSHALL);
12if (∗mp->b_rptr & FLUSHW)
13flushq(q, FLUSHALL);
14putnext(q, mp);
15break;
. . .
16}
17 }

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