Re: protected type interrupts

REH a écrit :

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?

The goal of the "potentially blocking" rule is to prevent *unbounded* blocking. Short blockings, such as those require to provide mutual exclusion, are OK, because thay are bounded.

Think of it this way: if it can be implemented on a multi-processor by a simple spin-lock, it is not potentially blocking. If it requires a queue, and being awaken depends on some non determinable condition, it is potentially blocking.
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J-P. Rosen (rosen@xxxxxxxxx)
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