System V msg queue bugs in latest kernels

[Mark Swanson <swansma@yahoo.com>]

Hello,

ipcs (msg) gives incorrect results if used-bytes is above 65536. It
stays at 65536 even though messages are being read and removed from the
msg queue.

The sysv msg queue either ignores the /proc/sys/kernel/msgmnb value if
it is above 65536 or simply gets it wrong. Proof: I can place more than
msgmnb bytes in a queue. The behavior is not consistent, but 100%
reproducable. It's not consistent because if I use messages of about
1000-2000 bytes the msgmnb never gets bigger than 65536 (even if
/proc/sys/kernel/msgmnb is set to 1048576 - bug). However, if I use
small messages like 13 bytes I can get bizarre (wrong) ipcs results
like this:

used-bytes    messages
65536          65536


Why does Linux ignore the /proc/sys/kernel/msgmnb value - or seem to
partly ignore it if it is above 65536? I *really* need this to be
around a MB. Is there an undocumented limit here or is this a bug?

Thanks.





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A camel is ugly but useful; it may stink, and it may spit, but it'll get you where you're going. - Larry Wall -

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