07-30-2003
Hmmm....you do have a point. I was getting CBYTES mixed up with QBYTES.
I agree, for the most part, QNUM = 0 and CBYTES != 0 is not consistent. But I can think of one exception where it might make sense. When you do your msgsnd, you are setting msgflg to zero. That means that IPC_NOWAIT is turned off. The msgsnd system call checks to see if this message would exceed some limits. This includes a check of the message queue you are using as well as some system wide limits. If a msgsnd would exceed a limit and it did not set IPC_NOWAIT, the msgsnd system call will suspend until it is safe to send the message. I don't know what state the message queue is in during this suspension. It could well be that CBYTES has been increased but QNUM has not yet been incremented.
This would explain why it works for a few hours and then locks up. Reproduce the error and then run "ipcs -qa" and compare the total messages queue resources in use against your kernel parameters. If this is the problem, you will need to increase the kernel parameters. Or you may have a message queue leak somewhere.
That is my only idea. If it's not that, I would next suspect a broken kernel. You might check for any appropiate patches.
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LEARN ABOUT HPUX
tt_pattern_disposition_add
tt_pattern_disposition_add(library call) tt_pattern_disposition_add(library call)
NAME
tt_pattern_disposition_add -- add a value to the disposition field for a pattern
SYNOPSIS
#include <Tt/tt_c.h>
Tt_status tt_pattern_disposition_add(
Tt_pattern p,
Tt_disposition r);
DESCRIPTION
The tt_pattern_disposition_add function adds a value to the disposition field for the specified pattern.
The p argument is a unique handle for a message pattern. This handle is returned after tt_pattern_create(3) is called.
The r argument indicates whether an instance of the receiver is to be started to receive the message immediately, or whether the message is
to be queued until the receiving process is started at a later time or discarded if the receiver is not started. The following values are
defined:
TT_DISCARD
There is no receiver for this message. The message will be returned to the sender with the Tt_status field containing TT_FAILED.
TT_QUEUE Queue the message until a process of the proper ptype receives the message.
TT_START Attempt to start a process of the proper ptype if none is running.
TT_QUEUE+TT_START
Queue the message and attempt to start a process of the proper ptype if none is running.
RETURN VALUE
Upon successful completion, the tt_pattern_disposition_add function returns the status of the operation as one of the following Tt_status
values:
TT_OK The operation completed successfully.
TT_ERR_NOMP
The ttsession(1) process is not running and the ToolTalk service cannot restart it.
TT_ERR_POINTER
The pointer passed does not point to an object of the correct type for this operation.
SEE ALSO
Tt/tt_c.h - Tttt_c(5), tt_pattern_create(3).
tt_pattern_disposition_add(library call)