Re: cas latch
- From: "Stig Hornuff" <hornuff@xxxxxxxxxxx>
- To: norman.dunbar@xxxxxxxxxxxxxxxxxxxxxxxxx, Mark.Bobak@xxxxxxxxxxxxxxx, jonathan@xxxxxxxxxxxxxxxxxx
- Date: Tue, 31 Oct 2006 10:11:19 +0000
HPUX (PA-RISC 2.0), does not have test-and-set or compare-and-swap normally
needed by semaphore operations. BUT it does have a compare-and-clear
instruction by which the same thing can be achieved: A true atomic semaphore
----Original Message Follows----
From: "Norman Dunbar" <norman.dunbar@xxxxxxxxxxxxxxxxxxxxxxxxx>
To: <Mark.Bobak@xxxxxxxxxxxxxxx>, <jonathan@xxxxxxxxxxxxxxxxxx>
Subject: Re: cas latch
Date: Tue, 31 Oct 2006 08:34:37 +0000
>> Correct, HP doesn't do CAS.
So does that mean that HPUX doesn't have an atomic 'test and set'
machine code instruction then ?
If so, how on Earth can Oracle emulate one for the CAS latch. I'm of
the belief (but I'm easily led) that a latch operation has to be atomic
so that it cannot be interrupted half way through and hijacked by
The fact that HPUX doesn't has such an atomic instruction has caused my
brain to leak out through my ears trying to figure out a way of
implementing a latch in software with a process that cannot be
interrupted. All I can come up with is a disable interrupts at the start
and enable at the end.
Any clues gratefully received. (Purely for my own curiosity.)
Contract Oracle DBA.
Rivers House, Leeds.
Internal : 7 28 2051
External : 0113 231 2051
Information in this message may be confidential and may be legally
privileged. If you have received this message by mistake, please notify the
sender immediately, delete it and do not copy it to anyone else.
We have checked this email and its attachments for viruses. But you should
still check any attachment before opening it.
We may have to make this message and any reply to it public if asked to
under the Freedom of Information Act, Data Protection Act or for litigation.
Email messages and attachments sent to or from any Environment Agency
address may also be accessed by someone other than the sender or recipient,
for business purposes.
If we have sent you information and you wish to use it please read our terms
and conditions which you can get by calling us on 08708 506 506. Find out
more about the Environment Agency at www.environment-agency.gov.uk
Log på MSN Messenger direkte på nettet: http://webmessenger.msn.com
Other related posts: