Date: Fri, 12 Jun 2015 13:10:54 -0600 From: Ian Lepore <ian@freebsd.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: Maksim Yevmenkin <maksim.yevmenkin@gmail.com>, Andriy Gapon <avg@freebsd.org>, "current@freebsd.org" <current@freebsd.org> Subject: Re: obtaining a minidump from panic() called from NMI handler Message-ID: <1434136254.1415.47.camel@freebsd.org> In-Reply-To: <20150612185521.GE2080@kib.kiev.ua> References: <CAFPOs6qsFZKMVzLEDL5X77H6s5LoTjsc4SkMWgR0D_P8RQG4YQ@mail.gmail.com> <557B1905.80307@FreeBSD.org> <CAFPOs6p5yTvdbJXPOKXuagZxj%2Bu-pE3kt5fsCWCpPVj4vktO%2Bg@mail.gmail.com> <20150612185521.GE2080@kib.kiev.ua>
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On Fri, 2015-06-12 at 21:55 +0300, Konstantin Belousov wrote: > On Fri, Jun 12, 2015 at 11:49:01AM -0700, Maksim Yevmenkin wrote: > > Andriy, > > > > >> i have a question about obtaining minidump as result of panic() being > > >> called from nmi handler. basically, i have a way to trigger nmi, and, > > >> i would like to panic() system and obtain a minidump. > > >> > > >> i have modified isa_nmi() to appropriately inspect bits and return > > >> non-zero return code. i have turned off machdep.kdb_on_nmi knob (set > > >> it to zero). i have confirmed that amd64 trap() is called with correct > > >> T_NMI type. i've also confirmed that panic() is called from amd64's > > >> trap(). > > >> > > >> the issue i have is that system is rebooting too early. basically, it > > >> looks like minidump is started, but, for whatever reason, other cpus > > >> are not completely stopped (or may be they are panic()ing again) and > > >> system just reboots without having complete the minidump. > > >> > > >> the issue is not present when machdep.kdb_on_nmi is set to 1. in this > > >> case, system drops into ddb prompt and 'call doadump' works as > > >> expected. for various reasons i can not use ddb, and, would like to > > >> have system save nmi triggered minidump completely unattended. > > >> > > >> can someone please give me a clue as to what i should be looking into > > >> to make this work? > > > > > > could it be that more than one CPUs get the NMI at the same time? > > > > i guess, its possible. is there an easy way to check for that? > > > > > IF yes, then the current code wouldn't handle that well - each of the NMI-ed > > > CPUs will try to stop all others with another NMI and it will wait until each of > > > those CPUs sets an acknowledgement bit in its NMI handler. This scheme works > > > fine if there's only one CPU that wants to become the master, but results in a > > > deadlock otherwise. > > > > that makes sense. i don't observe deadlock, but, simple reboot. > > I believe I posted patches to serialize ddb entrance or panics due to nmi. > I do not have references handy, you could search lists. > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" That was on freebsd-arch in July 2014. -- Ian
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