POSIX Message Queues

[Steve]

Does anyone know of any way to change the limits WRT to POSIX message
queue creation, particularly
the maximum size of the queue entries and the maximum number of
messages in a queue?

Cheers Steve.

[Steve Watt]

In article <a30de0ef-7b5b-4e6f...@o6g2000yqj.googlegroups.com>,

Which interface, the antique draft 9 one or the final version? If the
final, I don't remember coding any limits in, except that it needs to be
able to create a shared memory segment the size of the entire queue.

Mind you, it's been over a decade, so it's possible the code I wrote
isn't in there anymore. But you didn't give a hint about versions.

Regards,
--
Steve Watt KD6GGD PP-ASEL-IA ICBM: 121W 56' 57.5" / 37N 20' 15.3"
Internet: steve @ Watt.COM Whois: SW32-ARIN
Free time? There's no such thing. It just comes in varying prices...

[Steve]

On Jul 26, 11:26 pm, Steve Watt <steve.removet...@Watt.COM> wrote:
> In article <a30de0ef-7b5b-4e6f-91b1-97c3b9dcd...@o6g2000yqj.googlegroups.com>,

Am using LynxOS 4.0 and 4.2. On further investigation you can set the
maximum
queue entries and size when creating the queue with mq_open. It's just
that you
can't subsequently modify them with mq_setattr.

BTW is there any way to view what queues have been created? On Linux
you
can mount the message queue fileystem to examine queues and contents.

Regards.

[Steve Watt]

In article <ecbd4ed8-1e73-4dfd...@18g2000yqa.googlegroups.com>,

Steve <st...@prismtech.com> wrote:
>On Jul 26, 11:26�pm, Steve Watt <steve.removet...@Watt.COM> wrote:
>> In article <a30de0ef-7b5b-4e6f-91b1-97c3b9dcd...@o6g2000yqj.googlegroups.com>,
>>
>> Steve �<st...@prismtech.com> wrote:
>> >Does anyone know of any way to change the limits WRT to POSIX message
>> >queue creation, particularly
>> >the maximum size of the queue entries and the maximum number of
>> >messages in a queue?
>>
>> Which interface, the antique draft 9 one or the final version? �If the
>> final, I don't remember coding any limits in, except that it needs to be
>> able to create a shared memory segment the size of the entire queue.
>>
>> Mind you, it's been over a decade, so it's possible the code I wrote
>> isn't in there anymore. �But you didn't give a hint about versions.
>>
>

>Am using LynxOS 4.0 and 4.2. On further investigation you can set
>the maximum queue entries and size when creating the queue with
>mq_open. It's just that you can't subsequently modify them with
>mq_setattr.

Resizing POSIX message queues in a realtime system is going to require
a complete teardown and recreate of the queue. Part of the point of
completely preallocating the queue is to provide run-time determinism.

>BTW is there any way to view what queues have been created? On Linux
>you can mount the message queue fileystem to examine queues and
>contents.

They should show up in "ipcs -q". How that command learns about them
is Dark Magick(TM), and (more importantly) will vary between releases.

[Thomas Mueller]

On Wed, 29 Jul 2009 22:24:00 +0000, Steve Watt wrote:
> In article
> <ecbd4ed8-1e73-4dfd...@18g2000yqa.googlegroups.com>,
> Steve <st...@prismtech.com> wrote:
>>BTW is there any way to view what queues have been created? On Linux you
>>can mount the message queue fileystem to examine queues and contents.
>
> They should show up in "ipcs -q". How that command learns about them is
> Dark Magick(TM), and (more importantly) will vary between releases.

"lipcs" is the one for POSIX.1b IPC ("ipcs" is for System-V compatible
IPC).

--
Thomas