Date: Sat, 13 Jun 2015 21:17:19 +0800 From: Julian Elischer <julian@freebsd.org> To: Maksim Yevmenkin <maksim.yevmenkin@gmail.com>, Andriy Gapon <avg@freebsd.org> Cc: "current@freebsd.org" <current@freebsd.org> Subject: Re: obtaining a minidump from panic() called from NMI handler Message-ID: <557C2D5F.4080005@freebsd.org> In-Reply-To: <CAFPOs6p5yTvdbJXPOKXuagZxj%2Bu-pE3kt5fsCWCpPVj4vktO%2Bg@mail.gmail.com> References: <CAFPOs6qsFZKMVzLEDL5X77H6s5LoTjsc4SkMWgR0D_P8RQG4YQ@mail.gmail.com> <557B1905.80307@FreeBSD.org> <CAFPOs6p5yTvdbJXPOKXuagZxj%2Bu-pE3kt5fsCWCpPVj4vktO%2Bg@mail.gmail.com>
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On 6/13/15 2:49 AM, 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? hard code checks in the code so that all except the first do something different. (even only as a debug check).. like write to some location and loop... > >> 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. > > thanks, > max > _______________________________________________ > 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" > >
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