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Date: Wed, 08 Jan 2014 18:29:59 +0200
From: Andriy Gapon <avg@FreeBSD.org>
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To: Adrian Chadd <adrian@FreeBSD.org>,
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Subject: Re: Acquiring a lock on the same CPU that holds it - what can be done?
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I am sure that the following approach was suggested before, but I can not find
any references now.
So, the idea is to auto-associate a priority with a lock.  Every time a priority
lending would kick in we would record the priority in the lock.  The next time a
thread with a lower priority acquires that lock we would automatically boost the
thread to the recorded priority until it releases the lock.  This should prevent
the situation that you've described where a higher priority thread preempts a
lower priority thread just to discover that it holds a required lock and
priority lending is required before relinquishing a CPU to the preempted thread.

I am sure that there could be downsides to this approach.
-- 
Andriy Gapon