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Date:      Tue, 24 Feb 2015 11:03:42 -0700
From:      Warner Losh <imp@bsdimp.com>
To:        John-Mark Gurney <jmg@funkthat.com>
Cc:        Konstantin Belousov <kostikbel@gmail.com>, Harrison Grundy <harrison.grundy@astrodoggroup.com>, freebsd-arch@freebsd.org
Subject:   Re: locks and kernel randomness...
Message-ID:  <1E4A5E62-6E06-48BA-B5C5-9BD05811CDEF@bsdimp.com>
In-Reply-To: <20150224174053.GG46794@funkthat.com>
References:  <20150224012026.GY46794@funkthat.com> <20150224015721.GT74514@kib.kiev.ua> <54EBDC1C.3060007@astrodoggroup.com> <20150224024250.GV74514@kib.kiev.ua> <DD06E2EA-68D6-43D7-AA17-FB230750E55A@bsdimp.com> <20150224174053.GG46794@funkthat.com>

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> On Feb 24, 2015, at 10:40 AM, John-Mark Gurney <jmg@funkthat.com> =
wrote:
>=20
> Warner Losh wrote this message on Tue, Feb 24, 2015 at 07:56 -0700:
>> Then again, if you want to change random(), provide a weak_random() =
that???s
>> the traditional non-crypto thing that???s fast and lockless. That =
would make it easy
>> to audit in our tree. The scheduler doesn???t need cryptographic =
randomness, it
>> just needs to make different choices sometimes to ensure its notion =
of fairness.
>=20
> I do not support having a weak_random...  If the consumer is sure
> enough that you don't need a secure random, then they can pick an LCG
> and implement it themselves and deal (or not) w/ the locking issues...
>=20
> It appears that the scheduler had an LCG but for some reason the =
authors
> didn't feel like using it here..

Why don=E2=80=99t you support having a common random routine that=E2=80=99=
s to mix the
pot, but not cryptographically secure? Lots of algorithms use them, and =
having
a common one would keep us from reinventing the wheel.

Warner





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