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From: Ryan Stone <rysto32@gmail.com>
Date: Thu, 9 Feb 2017 13:02:43 -0500
Message-ID: <CAFMmRNzr=bScqvWCpDqHvqhdmZJBEPt5_jy1CjVtfxUvSZ8KHQ@mail.gmail.com>
Subject: [PATCH] Check for preemption after lowering a thread's priority
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I've just put up a phabricator review for a fix to ULE and 4BSD for a
priority inversion problem.  The issue is that after a running thread's
priority is lowered (usually due to releasing a mutex and having a priority
load revoked), the scheduler does not check whether the thread should now
be preempted by a thread waiting in the runq.  See this old ML post for a
detailed description of one instance that I saw:

https://lists.freebsd.org/pipermail/freebsd-current/2013-January/039261.html

The review can be found here:
https://reviews.freebsd.org/D9518