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List:       openjdk-nio-dev
Subject:    JDK 10 RFR of 8184157: (ch) AsynchronousFileChannel hangs with internal error when reading locked fi
From:       Brian Burkhalter <brian.burkhalter () oracle ! com>
Date:       2017-07-24 22:54:55
Message-ID: B5718195-0CF8-4FAC-8985-72464164127B () oracle ! com
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https://bugs.openjdk.java.net/browse/JDK-8184157
http://cr.openjdk.java.net/~bpb/8184157/webrev.00/

This problem is caused by a race condition wherein the PendingFuture of =
a lock operation in the PendingIoCache is replaced by that of a read =
operation, with both using the same key, before the completion status of =
the lock operation is dequeued by the event handler thread of Iocp. When =
the lock completion status is dequeued, the event handler looks up its =
corresponding PendingFuture but retrieves that of the read operation =
instead. This causes the completed() callback of the read task to be =
invoked with the NumberOfBytes transferred for the lock operation which =
is a garbage value. This results in an attempt to set the read =
ByteBuffer position to a value outside its permitted range.

The proposed solution is to introduce an invalidate() method on the =
PendingIoCache which removes the entry corresponding to the OVERLAPPED =
pointer from the map of overlapped-to-PendingFuture entries and places =
the OVERLAPPED pointer value in a Set where it remains until remove() is =
called. This ensures that the OVERLAPPED pointer map key will not be =
used for a PendingFuture to which it does not correspond. The pointer =
values of invalidated PendingFutures are removed from the Set when =
remove() is called in the Iocp event handler after the corresponding =
completion status is dequeued. All existing regression tests pass with =
this patch applied.

Thanks,

Brian=
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