Date: Wed, 3 Apr 2019 18:11:19 +0200 From: Michael Tuexen <tuexen@freebsd.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: Bruce Evans <brde@optusnet.com.au>, freebsd-hackers Hackers <freebsd-hackers@freebsd.org>, FreeBSD PowerPC ML <freebsd-ppc@freebsd.org> Subject: Re: powerpc64 head -r344018 stuck sleeping problems: th->th_scale * tc_delta(th) overflows unsigned 64 bits sometimes [patched failed] Message-ID: <8184C845-7721-4F88-974E-3F63F1980FDE@freebsd.org> In-Reply-To: <20190403070045.GW1923@kib.kiev.ua> References: <20190303161635.GJ68879@kib.kiev.ua> <20190304043416.V5640@besplex.bde.org> <20190304114150.GM68879@kib.kiev.ua> <20190305031010.I4610@besplex.bde.org> <20190306172003.GD2492@kib.kiev.ua> <20190308001005.M2756@besplex.bde.org> <20190307222220.GK2492@kib.kiev.ua> <20190309144844.K1166@besplex.bde.org> <20190324110138.GR1923@kib.kiev.ua> <E0785613-2B6E-4BB3-95CD-03DD96902CD8@fh-muenster.de> <20190403070045.GW1923@kib.kiev.ua>
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> On 3. Apr 2019, at 09:00, Konstantin Belousov <kostikbel@gmail.com> = wrote: >=20 > On Wed, Apr 03, 2019 at 12:27:32AM +0200, Michael Tuexen wrote: >>> On 24. Mar 2019, at 12:01, Konstantin Belousov <kostikbel@gmail.com> = wrote: >>>=20 >>> On Sat, Mar 09, 2019 at 06:00:14PM +1100, Bruce Evans wrote: >>>> I more strongly disclike (sic) the more complete merge. The = central APIs >>>> have even more parameters and reduced type safety to describe = objects as >>>> (offset, size) pairs. >>> I changed the patch to be type-safe. Now I like it even more. It = provides >>> 1. internal >>> 2. concise >>> 3. type-safe >>> API to fetch data from timehands. The implementation needs to be = read >>> only once. >> Hi, >>=20 >> I'm a bit lost... I think this started to fix a problem on G5 = PowerMacs. >> Do you think this patch solves the problem. Should this be tested? >> Or is this still work in progress or a general improvement not = necessary >> fixing the problem on G5 PowerMacs? >=20 > It started from a report of issues on G5. The specific issues are > bugs on G5, and the posted patches do not fix them. =46rom what I = see, > the timecounter values were wrapped. This is genuine ppc or G5 issue. Thanks a lot for the clarification. Best regards Michael >=20 > The patch fixes time keeping subsystem reaction to the already > bad situation, by correctly handling overflow in calculations. This > overflow can occur in more reasonable setups as well, e.g. if ddb was > activated and interrupts were stopped for prolonged period, even on = x86. >=20 > In addition, my version of the patch reorganizes the code and removes > excessive copies of the most delicate loops in lock-less readers. This > chunk can be split from the overflow part, but it is not completely > trivial.
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