6097f3451c
While it is true that the new vmspace passed to vmspace_switch_aio will always have a valid reference due to the AIO job or the extra reference on the original vmspace in the worker thread, it is not true that the old vmspace being switched away from will have more than one reference. Specifically, when a process with queued AIO jobs exits, the exit hook in aio_proc_rundown will only ensure that all of the AIO jobs have completed or been cancelled. However, the last AIO job might have completed and woken up the exiting process before the worker thread servicing that job has switched back to its original vmspace. In that case, the process might finish exiting dropping its reference to the vmspace before the worker thread resulting in the worker thread dropping the last reference. Reported by: np Reviewed by: alc, markj, np, imp MFC after: 2 weeks Sponsored by: Chelsio Communications Differential Revision: https://reviews.freebsd.org/D20542
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