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1. Programming
Hello !!!!! I have a simple question but i can't find the answer anywhere hope to meet it here.
Why it is a bad idea to pass pointers through message queues ?
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For... (2 Replies)
Discussion started by: qlyine
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2. Programming
Hi all,
I need help about message queues, i have a server-client program that communicates each other via msg queue, firstly server opens its msg queue and waits for msg then client opens server msg queue and its own msg queue(for receiving msg from server,clients sends msg to server msg... (7 Replies)
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3. Programming
Hii can anyone pls tell how to limit the max no of message in a posix message queue. I have made changes in proc/sys/fs/mqueue/msg_max
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4. Programming
Hello,
i need to write a message queue "chat server", that should work only localy.
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5. Programming
hi all...
ive been trying this program where i spawn 4 threads... and i am trying to use message queue to send msgs from 3 of the threads to the parent thread... but it doent seem to be working... ive almost pulled out my hair tryin to fix the prob :confused:
another wierd thing... (1 Reply)
Discussion started by: strider
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6. IP Networking
I am sending and retriving the message to the queue
the problem is
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so i want to retieve this garbage value and also want to know its size
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7. Programming
Is there any way one can delete , say , a particular message from a message queue on system V? (2 Replies)
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8. Programming
hi all,
I'm working on this problem for 2 days. Can somebody tell me that how to delete all message queues from the system ?
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9. Programming
Hi there:
Thanks first. When I use a message queue amony severl processes, will I have to synchronize the queue? I don't think I would have to because a message queue is implemented in a link listed. Correct me If I am wrong... (0 Replies)
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10. UNIX for Advanced & Expert Users
Hi,
I am working closly with unix message queues i have encountered the following -
after creating the Q and start working with it (pushing & pulling) i receive the following stange parameters on the q's -
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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
rmvq() 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
rmvq() can be called from user or interrupt 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 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 ALSO
freemsg(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 system panic.
SunOS 5.10 9 Jul 2001 rmvq(9F)
