RMVQ(9F)RMVQ(9F)NAMErmvq - 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 con‐
text.
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 mes‐
sage (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 ALSOfreemsg(9F), getq(9F), insq(9F)
Writing Device Drivers
STREAMS Programming Guide
WARNINGS
Make sure that the message mp is linked onto q to avoid a possible sys‐
tem panic.
Jan 16, 2006 RMVQ(9F)
