svn commit: r243764 - head/sys/x86/x86

[Andriy Gapon]

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 <longwitz at incore.de>
  Tested by:	Andreas Longwitz <longwitz at incore.de>
  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