Date: Sun, 25 Nov 2012 14:55:33 +0200 From: Andriy Gapon <avg@FreeBSD.org> To: attilio@FreeBSD.org Cc: freebsd-hackers@FreeBSD.org, Ryan Stone <rysto32@gmail.com> Subject: Re: stop_cpus_hard when multiple CPUs are panicking from an NMI Message-ID: <50B21545.5060807@FreeBSD.org> In-Reply-To: <CAJ-FndADxJtYPX2-cQnqJoLhzYtJMidG1DPPY%2B6Dtf4rVw_zrw@mail.gmail.com> References: <CAFMmRNwb_rxYXHGtXgtcyVUJnFDx5PSeMmA_crBbeV_rtzL9Cg@mail.gmail.com> <50A5F12C.1050902@FreeBSD.org> <CAJ-FndAB%2B7KRAE91L9634eXgzqgrizwtwCBC7AAg%2B0EX89TEBQ@mail.gmail.com> <50A63D1D.9090500@FreeBSD.org> <CAJ-FndDC1QCytXDJqVkism_5VoLNo_OzZxNEQ9NHx63HC=GTNg@mail.gmail.com> <50A65208.4050804@FreeBSD.org> <CAJ-FndADxJtYPX2-cQnqJoLhzYtJMidG1DPPY%2B6Dtf4rVw_zrw@mail.gmail.com>
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on 25/11/2012 14:29 Attilio Rao said the following: > I think the patch you propose makes such effects even worse, because > it disables interrupts in generic_stop_cpus(). > What I suggest to do, is the following: > - The CPU which wins the race for generic_stop_cpus also signals the > CPUs it is willing to stop on a global mask > - Another CPU entering generic_stop_cpus() and loosing the race, > checks the mask of cpus which might be stopped and stops itself if > necessary (ie. not yet done). We must be careful with races here, but > I'm confindent this can be done easily enough. I think that you either misunderstood my patch or I misunderstand your suggestion, because my patch does exactly what you wrote above. -- Andriy Gapon
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