Re: protected type interrupts

["REH" <spamjunk@stny.rr.com>]

Adam Beneschan wrote:
> REH wrote:
>
> > Thanks for the reference.  Is your work-around valid?  Isn't calling
> > Relay_Object.Isr a potentially blocking operation, and thus a bad thing
> > to do in an interrupt?
>
> I don't think it's potentially blocking... Relay_Object.Isr is a
> procedure, and as I read 9.5.1, a call to a protected *procedure* is
> not a potentially blocking operation unless it's done from the same
> protected object.  A call on a protected *entry* would be potentially
> blocking.  [This is from the Ada 95 manual.  If this has changed in Ada
> 0Y, I can't tell because www.adaic.com isn't responding.]
>

I don't understand.  How can a procedure within a protected object
modify data internal to the object in a thread-safe way without the
potentially blocking effect of enforcing mutual exclusion?  If one task
is "using" the object, and another calls one of the object's
procedures, would the second task not be blocked until the first one
exits the object?  

REH