3d5
Subj : Re: Improving read-write lock
To   : comp.programming.threads
From : David Schwartz
Date : Wed Feb 16 2005 12:18 pm


"Marcin 'Qrczak' Kowalczyk" <qrczak@knm.org.pl> wrote in message 
news:87y8dol8tj.fsf@qrnik.zagroda...
> "Joe Seigh" <jseigh_01@xemaps.com> writes:
>
>>> It's not a perfect situation of course, because only one ReadPromotable
>>> lock exists.
>>
>> More than one promotable read lock can exist.  It just has to stay 
>> blocked
>> until any pior promotable read locks have completed their write access.
>
> No, because if two threads holding promotable read locks try to
> promote them, they will deadlock.
>
> Unless you meant a different semantics where promotion may allow other
> writers to invervene. I think .NET provides something like this (with
> a semi-reliable check whether some writer did actually intervene).

    If it does that, it's precisely equivalent to a read unlock followed by 
a write lock.

    DS

.

0