Re: svn commit: r243764 - head/sys/x86/x86
on 06/12/2012 22:40 John Baldwin said the following: > 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? > Will do. -- Andriy Gapon ___ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
Re: svn commit: r243764 - head/sys/x86/x86
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 ___ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
svn commit: r243764 - head/sys/x86/x86
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. Reported by: Andreas Longwitz Tested by:Andreas Longwitz MFC after:12 days Modified: head/sys/x86/x86/io_apic.c Modified: head/sys/x86/x86/io_apic.c == --- head/sys/x86/x86/io_apic.c Sat Dec 1 18:13:53 2012(r243763) +++ head/sys/x86/x86/io_apic.c Sat Dec 1 18:16:14 2012(r243764) @@ -311,12 +311,12 @@ ioapic_program_intpin(struct ioapic_ints } /* Write the values to the APIC. */ - intpin->io_lowreg = low; - ioapic_write(io->io_addr, IOAPIC_REDTBL_LO(intpin->io_intpin), low); value = ioapic_read(io->io_addr, IOAPIC_REDTBL_HI(intpin->io_intpin)); value &= ~IOART_DEST; value |= high; ioapic_write(io->io_addr, IOAPIC_REDTBL_HI(intpin->io_intpin), value); + intpin->io_lowreg = low; + ioapic_write(io->io_addr, IOAPIC_REDTBL_LO(intpin->io_intpin), low); } static int ___ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
