1rmvq(9F) Kernel Functions for Drivers rmvq(9F)
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6 rmvq - remove a message from a queue
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9 #include <sys/stream.h>
10 void rmvq(queue_t *q, mblk_t *mp);
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17 Architecture independent level 1 (DDI/DKI).
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20 q Queue containing the message to be removed.
21 mp Message to remove.
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27 The rmvq() function removes a message from a queue. A message can be
28 removed from anywhere on a queue. To prevent modules and drivers from
29 having to deal with the internals of message linkage on a queue, either
30 rmvq() or getq(9F) should be used to remove a message from a queue.
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33 The rmvq() function can be called from user, interrupt, or kernel con‐
34 text.
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37 This code fragment illustrates how one may flush one type of message
38 from a queue. In this case, only M_PROTO T_DATA_IND messages are
39 flushed. For each message on the queue, if it is an M_PROTO message
40 (line 8) of type T_DATA_IND (line 10), save a pointer to the next mes‐
41 sage (line 11), remove the T_DATA_IND message (line 12) and free it
42 (line 13). Continue with the next message in the list (line 19).
43 1 mblk_t *mp, *nmp;
45 2 queue_t *q;
46 3 union T_primitives *tp;
47 4
48 5 /* Insert code here to protect queue and message block */
49 6 mp = q->q_first;
50 7 while (mp) {
51 8 if (mp->b_datap->db_type == M_PROTO) {
52 9 tp = (union T_primitives *)mp->b_rptr;
53 10 if (tp->type == T_DATA_IND) {
54 11 nmp = mp->b_next;
55 12 rmvq(q, mp);
56 13 freemsg(mp);
57 14 mp = nmp;
58 15 } else {
59 16 mp = mp->b_next;
60 17 }
61 18 } else {
62 19 mp = mp->b_next;
63 20 }
64 21 }
65 22 /* End of region that must be protected */
66 When using rmvq(), you must ensure that the queue and the message block
70 is not modified by another thread at the same time. You can achieve
71 this either by using STREAMS functions or by implementing your own
72 locking.
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75 freemsg(9F), getq(9F), insq(9F)
76 Writing Device Drivers
79 STREAMS Programming Guide
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84 Make sure that the message mp is linked onto q to avoid a possible sys‐
85 tem panic.
86SunOS 5.11 16 Jan 2006 rmvq(9F)