Properly release locks in lamina.core.graph.node/propagate
#45
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Previously, exceptions raised in `lamina.core.graph.node/propagate` could lead to a node's lock to not be released properly because releasing didn't happen in a `finally` clause. However, using the `with-lock` macro is not possible in this case because in some branches the lock is released before the `with-lock` body ends. To allow for this, a `with-lock*` macro is introduced. If the lock is released inside its body it will refrain from unlocking it again. To support this, `locked?` is added to `ILock` which checks whether a lock is currently held. Also, recurring from inside a `try` form is not allowed but would be required in this case for traversing a chain of nodes. Thus the nodes traversal loop is changed to recur from outside the `try` form.
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Any news on this one? :-) |
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Wow, this completely fell off my radar. I'm flying out to the Conj today, On Wed, Nov 14, 2012 at 6:22 AM, Moritz Heidkamp
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⏰ Another bi-monthly issue reminder :-) |
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Hey, I've actually been looking at this, trying to understand where there's the possibility of an exception. I found one in queue.clj, but not in the propagate method in node.clj. Before making the inner loop that much more complicated, I want to understand what's happened. Just out of curiosity, have you seen this again? |
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I don't think I've seen it again since then. One scenario which I think could cause this is when a thread is stopped while we're in |
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Were you calling Thread.stop()? |
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Not explicitly but I might have been |
Previously, exceptions raised in
lamina.core.graph.node/propagatecould lead to a node's lock to not be released properly because
releasing didn't happen in a
finallyclause. However, using thewith-lockmacro is not possible in this case because in somebranches the lock is released before the
with-lockbody ends. Toallow for this, a
with-lock*macro is introduced. If the lock isreleased inside its body it will refrain from unlocking it again. To
support this,
locked?is added toILockwhich checks whether alock is currently held. Also, recurring from inside a
tryform isnot allowed but would be required in this case for traversing a chain
of nodes. Thus the nodes traversal loop is changed to recur from
outside the
tryform.I'm not sure if this is the best way to fix the root problem, so feel
free to implement a better solution instead.
Oh, and I threw out some unnecessary
doforms fromwith-lockand
with-exclusive-lockwhile I was at it :-)