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: > > 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. > > 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... > > It appears that the scheduler had an LCG but for some reason the authors > didn't feel like using it here.. Why don’t you support having a common random routine that’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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