[Info-vax] Internals questions

[VAXman- at SendSpamHere.ORG]

In article <3vpyl.192413$ot7.23137 at newsfe15.ams2>, "Ade" <adrian.birkett at blueyonder.co.uk> writes:
>Hi,
>
>Is it possible to look at the contents of a mailbox device within SDA 
>without removing them? If so, how?.

YES.  Get yourself a copy of the OpenVMS Internals and Data Structures 
(I&DS) and learn the mechanics of I/Os queued to a particular mailbox.
Also, I could recommend you GOOGLE for an SDA extension for this.  I'm
pretty certain that someone has published this.  

To get you started:
SDA> SHOW DEVICE MBAn
SDA> EXAM @(UCB+UCB$L_MB_MSGQFL)

I do not believe there is a definition for the mailbox message block.
I would use SHOW STACK @(UCB+UCB$L_MB_MSGQFL);length  or get the I&DS
and define your own.  The size of the block is in the usual location.

 
>Also, how do I view the status of a common event flag cluster in SDA?

Again, read the OpenVMS I&DS

I'm not sure what you mean by status, however.  

Common EF are queued off of SCH$GQ_CEBHD.
Find your CEB.  Then look at the wait queue count for a non-zero value.
The PCBs of processes waiting on such flags will be queue to the CEB.
In the PCB you can see the flags at PCB$L_EFC{2/3}P

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