Question about threading implications of specification
cowwoc at bbs.darktech.org
Tue Jul 12 08:00:45 PDT 2011
The specification for AsynchronousByteChannel.read() talks about the
operation taking place asynchronously, but what happens when the end of
stream has been reached? Is an implementation allowed to fire the completion
handler (or set the future) within the thread that invoked read()? From the
implementation's point of view, there is no reason to carry out this
operation asynchronously, because we already know the result. A similar case
occurs if a user attempts to read into a buffer where remaining() returns 0
(so we know the read operation must return 0).
I ask because I've run into a race condition in my implementation. I'm
invoking a completion handler that invokes notify() on itself when the
operation completes. I then invoke the following user code:
Note the user is assuming that the handler will be notified when the
operation completes, but because read() runs synchronously at end of stream
the handler gets notified before wait() and the latter will block forever.
Does the specification require me to update Future/CompletionHandler in a
separate thread or should users be aware of the fact that the thread that
invokes read() may update said objects itself?
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