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Code Issues Releases Activity

ioapic_program_intpin: program high bits before low bits

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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 <longwitz@incore.de>
Tested by:	Andreas Longwitz <longwitz@incore.de>
MFC after:	12 days
This commit is contained in:
Andriy Gapon 2012-12-01 18:16:14 +00:00
parent 289b3b96ac
commit ff08349df5
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=243764
1 changed files with 2 additions and 2 deletions
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4
sys/x86/x86/io_apic.c
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@ -311,12 +311,12 @@ ioapic_program_intpin(struct ioapic_intsrc *intpin)
}
/* 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