From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: possible recursive locking issue
Date: Fri, 7 Jul 2017 09:54:13 +0200
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On 06/07/2017 23:10, Alex Williamson wrote:
> vfio_unpin_pages() also takes a read-lock on
> the same.  Why is this a problem?  We should be able to nest
> read-locks.

rwsem is fair in that it blocks out new readers if a writer is waiting.
In this case nesting causes a deadlock, because the outer read-lock will
never be released.

Paolo