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From: "Chris Sparks (Mr. Ada)" <sparks@NFS.AISF.COM>
Subject: Re: Recursive Protected types getting deadlocked!
Date: 1997/09/09
Message-ID: <341560D3.711A@aisf.com>#1/1
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Sender: Ada programming language <INFO-ADA@LISTSERV.NODAK.EDU>
References: <199709090355.UAA29772@wanchai.aisf.com>
Comments: Gated by NETNEWS@AUVM.AMERICAN.EDU
Organization: Boeing
Newsgroups: comp.lang.ada
Date: 1997-09-09T00:00:00+00:00
List-Id: <comp.lang.ada>


Tucker Taft wrote:

> > Dale Stanbrough (dale@goanna.cs.rmit.EDU.AU) wrote:
> >
> > : I've written a small semaphore that records the task id of the owner,
> > : allowing recusive lock taking (i'm looking at how Java tasking works).
> >
> > : The following code seems to deadlock however. It seems that when a
> > : 2nd task is woken up on the Queued entry, it does so in the context
> > : of the first Task (or so the Image function tells me...).
> >
> > : This to me seems very strange. Is it likely to be an error in Gnat,
> > : or is it a misunderstanding on my part as to how this all works...
> >
> Any "convenient" thread may perform an entry body (RM95 9.5.3(22)).
> This flexibility can be critical to minimizing unnecessary context
> switches and lock transfers.  Hence, asking for "Current_Task" from
> inside an entry body is not useful.  If you need to get the
> identity of the thread which initiated an entry call, use
> the 'Caller attribute (C.7.1(14)).
>
> For example, inside Seize you should use "Seize'Caller"
> rather than "Current_Task"; inside Release you should use
> "Release'Caller".

Release is a procedure not an entry.  Maybe you meant the entry "Queue".

Chris Sparks