Date: Mon, 14 Jan 2013 01:18:32 +0200 From: Alexander Motin <mav@FreeBSD.org> To: Ian Lepore <freebsd@damnhippie.dyndns.org> Cc: Davide Italiano <davide@freebsd.org>, freebsd-arch@freebsd.org, FreeBSD Current <freebsd-current@freebsd.org>, Marius Strobl <marius@alchemy.franken.de> Subject: Re: [RFC/RFT] calloutng Message-ID: <50F340C8.2040905@FreeBSD.org> In-Reply-To: <1358118601.32417.41.camel@revolution.hippie.lan> References: <50CCAB99.4040308@FreeBSD.org> <50CE5B54.3050905@FreeBSD.org> <50D03173.9080904@FreeBSD.org> <20121225232126.GA47692@alchemy.franken.de> <50DB4EFE.2020600@FreeBSD.org> <20130106152313.GD26039@alchemy.franken.de> <50EBF921.2000304@FreeBSD.org> <20130113180940.GM26039@alchemy.franken.de> <50F30CAB.3000001@FreeBSD.org> <1358118601.32417.41.camel@revolution.hippie.lan>
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On 14.01.2013 01:10, Ian Lepore wrote: > On Sun, 2013-01-13 at 21:36 +0200, Alexander Motin wrote: >> On 13.01.2013 20:09, Marius Strobl wrote: > [...] >>> >>> Uhm, there are no NMIs on sparc64. Does it make sense to bypass this >>> adjustment on sparc64? >> >> If it is not possible or not good to to stop timer during programming, >> there will always be some race window between code execution and timer >> ticking. So some minimal safety range should be reserved. Though it >> probably can be significantly reduced. In case of x86/HPET there is >> additional factor of NMI, that extends race to unpredictable level and >> so makes additional post-read almost mandatory. >> >>>> May be with rereading counter >>>> after programming comparator (same as done for HPET, reading which is >>>> probably much more expensive) this value could be reduced. >>> >>> I see. There are some bigger fish to fry at the moment though :) >> > > Speaking of the HPET code, it seems to me that its restart logic can > fire the same event twice. Is that harmless? It is much less harmful then not fire and loose interrupt completely, and as result stuck for indefinite time. I have no better ideas, while this seems works well. -- Alexander Motin
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