Date: Wed, 25 Feb 2015 02:23:34 -0800 From: Harrison Grundy <harrison.grundy@astrodoggroup.com> To: freebsd-arch@freebsd.org Subject: Re: locks and kernel randomness... Message-ID: <54EDA2A6.9080209@astrodoggroup.com> In-Reply-To: <20150225102113.GD74514@kib.kiev.ua> References: <20150224231921.GQ46794@funkthat.com> <1424822522.1328.11.camel@freebsd.org> <20150225002956.GT46794@funkthat.com> <2F49527F-2F58-4BD2-B8BE-1B1190CCD4D0@bsdimp.com> <54ED5656.50607@astrodoggroup.com> <20150225090638.GB74514@kib.kiev.ua> <54ED92E5.4010803@astrodoggroup.com> <54ED9A4B.4060802@astrodoggroup.com> <20150225100512.GC74514@kib.kiev.ua> <54EDA128.4000107@astrodoggroup.com> <20150225102113.GD74514@kib.kiev.ua>
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On 02/25/15 02:21, Konstantin Belousov wrote: > On Wed, Feb 25, 2015 at 02:17:12AM -0800, Harrison Grundy wrote: >> >> >> On 02/25/15 02:05, Konstantin Belousov wrote: >>> On Wed, Feb 25, 2015 at 01:47:55AM -0800, Harrison Grundy >>> wrote: >>>> Three choices here are attached here: >>>> >>>> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=197922 >>>> >>>> The only remaining one I don't have a patch for is putting a >>>> "real" PRNG in ULE. >>>> >>>> At this point, as far as ULE goes, It just comes down to >>>> picking from one of those approaches. >>> >>> The third patch, ' Creates sched_random, using the system used >>> in cpu_search.', seems to miss updating the dpcpu randomval in >>> sched_random(), isn't it ? >>> >> >> It does exactly what cpu_search does. > I do not see how it does exactly what cpu_search does. > > cpu_search is updating *rndptr: rnd = (*rndptr = *rndptr * 69069 + > 5) >> 26; > > while code in patch is: + rndptr = DPCPU_PTR(randomval); + > rnd = (*rndptr * 69069 + 5) >> 26; > > where is the write to *rndptr ? My mistake. I'll update the patch accordingly. Interestingly enough, ULE doesn't seem to care about losing randomness there either. --- Harrison
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