[concurrency-interest] difference latch and lock

David Holmes dcholmes at optusnet.com.au
Wed Aug 30 17:36:45 EDT 2006


Peter,

It may be that they are using "latch" as a lightweight internal lock. Pretty
poor choice of name if you ask me though.

Cheers,
David Holmes

> -----Original Message-----
> From: Peter Veentjer [mailto:alarmnummer at gmail.com]
> Sent: Thursday, 31 August 2006 7:32 AM
> To: dholmes at ieee.org
> Cc: concurrency-interest at cs.oswego.edu
> Subject: Re: [concurrency-interest] difference latch and lock
>
>
> Ps: a 'lock' in Oracle is something that is kept for a longer period
> of time (in most cases a lock is maintained untill the transaction
> completes).
>
> Maybe this is the reason why they have introduced Locks and Latches?
>
> A Latch is a Lock that is invisible from the outside and only locked
> for a small period of time (to prevent multiple threads screwing
> around with internal system structures)
>
> A (Database) Lock is a Lock that is visible from the outside. If I
> have locked a record, you can't update it untill I have released the
> lock.A Database lock prevent isolation problems: acid)
>
> Could that be the reason why there is a difference between Latches
> (internal Locks) and Locks (database locks)?
>
> On 8/30/06, Peter Veentjer <alarmnummer at gmail.com> wrote:
> > I don't know what a latch is supposed to do. I see the term in
> > documentation (especially in concurrency control documentation of
> > Oracle). And I think a Latch can be compared to a Lock, but I don't
> > know for sure and I can't find any usefull documentation about what a
> > Latch is supposed to do.
> >
> > So I want to know what it does.
> >
> > On 8/30/06, David Holmes <dcholmes at optusnet.com.au> wrote:
> > > Peter,
> > >
> > > Depends exactly what you mean by "latch". A latch or gate is a
> > > synchronization barrier that is either open or closed. If
> open anyone can
> > > pass, if closed no one can pass. A Lock is intended to let through one
> > > thread at a time.
> > >
> > > I don't know what they meant by a latch being more
> lightweight than a lock
> > > ???
> > >
> > > David Holmes
> > >
> > > > -----Original Message-----
> > > > From: concurrency-interest-bounces at cs.oswego.edu
> > > > [mailto:concurrency-interest-bounces at cs.oswego.edu]On
> Behalf Of Peter
> > > > Veentjer
> > > > Sent: Thursday, 31 August 2006 6:14 AM
> > > > To: concurrency-interest at cs.oswego.edu
> > > > Subject: [concurrency-interest] difference latch and lock
> > > >
> > > >
> > > > Who can tell me what the difference between a Latch and a Lock is. I
> > > > have read multiple times that a Latch is considered a more
> lightweight
> > > > lock than the lock (maybe only in the context of databases and heavy
> > > > weight locks).
> > > >
> > > > But in Java all Locks and synchronized blocks are
> lightweight.. so are
> > > > there differences?
> > > > _______________________________________________
> > > > Concurrency-interest mailing list
> > > > Concurrency-interest at altair.cs.oswego.edu
> > > > http://altair.cs.oswego.edu/mailman/listinfo/concurrency-interest
> > >
> > >
> >



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