[Libguestfs] question on nbdkit shutdown behavior

[Richard W.M. Jones]

A deeper problem I think is that it's ill-specified what is
supposed to happen when nbdkit receives a termination signal.
We don't specify (for example) that plugin callbacks could or
could not be killed in the middle.  Killing them in the middle
of a callback could be bad for some plugins.

Going back to the original problem, perhaps we could have fixed
it instead by acquiring a lock around all plugin callbacks, and
ensuring that plugin_cleanup also acquires the same lock.  The
lock would normally be uncontended so it shouldn't cause any
performance issues.  That would be a fairly simple revert of
63f0eb088 + alternate fix.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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