Date: Fri, 21 Aug 2015 20:10:48 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Julian Elischer <julian@freebsd.org> Cc: Ian Lepore <ian@freebsd.org>, freebsd-current <freebsd-current@freebsd.org> Subject: Re: freebsd-head: suddenly NMI panics lead to ddb being unable to stop CPUs? Message-ID: <20150821171048.GC2072@kib.kiev.ua> In-Reply-To: <55D7577B.8090000@freebsd.org> References: <CAJ-VmomvqULP--v47qKJisQkf8VQNvxEhXK=HXEtv9MuLz4D1g@mail.gmail.com> <CAFMmRNw6tWMQ-pfXzSpEM7kRgKafB9KnK-oUhWw2_E-P91drLw@mail.gmail.com> <55D74193.4020008@FreeBSD.org> <CAJ-Vmon6xXBSMPWgNhg-RZKLuuMDP1hvXG%2BDdZ3fZdvFnan06g@mail.gmail.com> <55D74402.70104@freebsd.org> <1440174193.242.279.camel@freebsd.org> <55D7577B.8090000@freebsd.org>
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On Sat, Aug 22, 2015 at 12:53:15AM +0800, Julian Elischer wrote: > On 8/22/15 12:23 AM, Ian Lepore wrote: > > On Fri, 2015-08-21 at 23:30 +0800, Julian Elischer wrote: > >> On 8/21/15 11:25 PM, Adrian Chadd wrote: > >>> Ah, cool. I'll give it a whirl. > >>> > >>> I'm a little worried about having all of the other cores spinning in > >>> this case (mostly thermal; the machines get VERY LOUD when the CPUs > >>> are spinning..) > >>> > >> make each spin with the pause instruction.. and for N seconds (N being > >> the CPU ID) or something > > cpu_spinwait() is defined as ia32_pause() on i386 and amd64. > > > > The problem is that ONLY x86 arches benefit from cpu_spinwait(), it's > > just a nop on other arches, which turn into little radiant heaters for > > long spins (like while waiting for APs to be released). > > remind me again why it cant spin with a 'halt' instruction? Because interrupts are disabled. Even NMI is disabled, because spin happens in the NMI handler. There is no way to wake up CPU from the halted state.home | help
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