Date: Thu, 6 Dec 2012 15:40:42 -0500 From: John Baldwin <jhb@freebsd.org> To: Andriy Gapon <avg@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r243764 - head/sys/x86/x86 Message-ID: <201212061540.42393.jhb@freebsd.org> In-Reply-To: <201212011816.qB1IGE2Y064317@svn.freebsd.org> References: <201212011816.qB1IGE2Y064317@svn.freebsd.org>
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On Saturday, December 01, 2012 1:16:14 pm Andriy Gapon wrote: > Author: avg > Date: Sat Dec 1 18:16:14 2012 > New Revision: 243764 > URL: http://svnweb.freebsd.org/changeset/base/243764 > > Log: > ioapic_program_intpin: program high bits before low bits > > Programming the low bits has a side-effect if unmasking the pin if it is > not disabled. So if an interrupt was pending then it would be delivered > with the correct new vector but to the incorrect old LAPIC. > > This fix could be made clearer by preserving the mask bit while > programming the low bits and then explicitly resetting the mask bit > after all the programming is done. > > Probability to trip over the fixed bug could be increased by bootverbose > because printing of the interrupt information in ioapic_assign_cpu > lengthened the time window during which an interrupt could arrive while > a pin is masked. Can you expand the comment to say that you write 'low' second since it may clear the masked bit? -- John Baldwin
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