Thanks Rob, Chris and Binyamin for your comments. I've learnt a lot from
them.
A couple of questions for the panel:
Chris, you said that:
"Using AX=1 and SSAR to another address space is not very clearly documented by IBM because it is a violation of the MVS xmemory architecture".
This comes as a surprise, as I've seen this used in many different programs.
Setting AX=1 will certainly allow you to access any address space's memory, but
unless you have another TCB needing to AXSET to something other than 1, I can't
see how this may not work, or could cause difficulties. Can you give more
details?
You also said that using ASC mode doesn't remove the need for the target address space to be swapped in. Short of a paging error, what could go wrong here?
Binyamin, you've suggested grabbing the LOCAL lock when the SSAR succeeds. Why
do you suggest this?
Thanks again for your comments.
David
David Stephens
Lead Systems Programmer
d...@longpelaexpertise.com.au
www.longpelaexpertise.com.au
<http://www.longpelaexpertise.com.au/images/logo.gif>
Longpela Expertise - System z Mainframe Consultants
Read new expert Mainframe articles every quarter in our LongEx Mainframe
Quarterly <http://www.longpelaexpertise.com.au/ezine>
Binyamin Dissen wrote:
On Mon, 14 Dec 2009 15:52:59 -0600 Chris Craddock <crashlu...@gmail.com>
wrote:
:>On Sun, Dec 13, 2009 at 8:49 PM, David Stephens <
:>d...@longpelaexpertise.com.au> wrote:
:>> This (very rough draft) article "Cross Memory Communications for Beginners"
:>> may help.
:>> http://www.longpelaexpertise.com.au/ezine/CrossMemoryBeginners.html
:>> David Stephens
:>> Lead Systems Programmer
:>> d...@longpelaexpertise.com.au
:>> www.longpelaexpertise.com.au <
:>> http://www.longpelaexpertise.com.au/images/logo.gif>
:>> Longpela Expertise - System z Mainframe Consultants
:>> Read new expert Mainframe articles every quarter in our LongEx Mainframe
:>> Quarterly <http://www.longpelaexpertise.com.au/ezine>
:>Corrections for the article;
:>(1) SRBs do NOT always run disabled. They are initially dispatched enabled
:>for interrupts just like any other piece of work. They only become disabled
:>(legally) if they obtain a spin lock such as the CPU lock. When they release
:>the lock they are reenabled (again, like any other piece of work)
:>(2) SRBs do not ALWAYS run before any TCB in the address space where they
:>are dispatched. SRBs that are scheduled into an enclave run at whatever
:>priority that enclave happens to be assigned at any given moment according
:>to the service goal and attainment. That priority could be higher (or LOWER)
:>than any other unit of work in the address space (both TCB and SRB)
:>(3) Using AX=1 and SSAR to another address space is not very clearly
:>documented by IBM because it is a violation of the MVS xmemory architecture.
:>You DO NEED that "complicated synchronous cross memory" code to be safe.
:>(4) ASC mode does not remove the need for the "other" address space to be
:>swapped in. You can't reliably access a swapped out address space. Most SVCs
:>fail with a S0F8 abend if called in AR mode.
:>...but not bad.
SRB's can be SUSPENDED (not exactly WAIT, but pretty close).
If IEAMSCHD is used, the SRB control block need not be created and the WAIT
can be automatic.
The ECB need not be in CSA - it merely must be HOME addressable from the
waiting address space.
When using SSAR, take the LOCAL LOCK of the target address space (if the SSAR
succeeds).
PT(I) sets the primary address space (but be very careful).
ALET 0 = primary (hardware)
ALET 1 = secondary (hardware)
ALET 2 = HOME (DU-AL)
The caller of the Basic PC must save the environment. The PC routine (by
convention) only restores R13. The caller must save whatever registers as well
as the SASN (if needed).
Any PC can call any other PC, basic or stacking.
They can be hooked,
--
Binyamin Dissen <bdis...@dissensoftware.com>
http://www.dissensoftware.com
Director, Dissen Software, Bar & Grill - Israel
Should you use the mailblocks package and expect a response from me,
you should preauthorize the dissensoftware.com domain.
I very rarely bother responding to challenge/response systems,
especially those from irresponsible companies.
----------------------------------------------------------------------
For IBM-MAIN subscribe / signoff / archive access instructions,
send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO
Search the archives at http://bama.ua.edu/archives/ibm-main.html
--
David Stephens
Lead Systems Programmer
d...@longpelaexpertise.com.au
www.longpelaexpertise.com.au
<http://www.longpelaexpertise.com.au/images/logo.gif>
Ph. 0404 757 821 (from Australia)
(Longpela Expertise Logo)
Longpela Expertise - System z Mainframe Consultants
Read new expert Mainframe articles every quarter in our LongEx Mainframe
Quarterly <http://www.longpelaexpertise.com.au/ezine>
----------------------------------------------------------------------
For IBM-MAIN subscribe / signoff / archive access instructions,
send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO
Search the archives at http://bama.ua.edu/archives/ibm-main.html
