RMVQ(9F) Kernel Functions for Drivers RMVQ(9F)
NAME
rmvq - remove a message from a queue
SYNOPSIS
#include <sys/stream.h>
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 message 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;
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 GuideWARNINGS
Make sure that the message
mp is linked onto
q to avoid a possible
system panic.
January 16, 2006 RMVQ(9F)
