On Wed, 8 Aug 2007 16:17:19 -0700 Aaron Durbin <[EMAIL PROTECTED]> wrote:
> In setup_APIC_timer with the HPET in use, a condition can arise while > waiting for the next irq slice to expire on the HPET which will either > cause an NMI watchdog to fire or a 3 minute busy loop if the NMI > watchdog is disabled. > > The HPET comparator and the counter keep incrementing during its normal > operation. When a comparison event fires the comparator will increment > by the designated period. If the HPET trigger occurs right after > the 'int trigger = hpet_readl(HPET_T0_CMP);' line, we will will spin > for up to 3 minutes (with a clock of 25MHz) waiting for the HPET > counter to wrap around. However, when the NMI watchdog is enabled the > NMI watchdog will detect a lockup and reboot the machine. This > scenario can be exasperated by the presence of an SMI which will > increase the window of opportunity for the condition to occur. > > The fix is to wait for the compartor to change which signals the > end of the tick slice. > > --- > > The last patch had a typo in the diff which really would cause the > problem state above. Sorry. > > diff --git a/arch/x86_64/kernel/apic.c b/arch/x86_64/kernel/apic.c > index 900ff38..06797e2 100644 > --- a/arch/x86_64/kernel/apic.c > +++ b/arch/x86_64/kernel/apic.c > @@ -791,10 +791,12 @@ static void setup_APIC_timer(unsigned in > > /* wait for irq slice */ > if (hpet_address && hpet_use_timer) { > + /* > + * Wait for the comparator value to change which signals that > + * the tick slice has expired. > + */ > int trigger = hpet_readl(HPET_T0_CMP); > - while (hpet_readl(HPET_COUNTER) >= trigger) > - /* do nothing */ ; > - while (hpet_readl(HPET_COUNTER) < trigger) > + while (trigger == hpet_readl(HPET_T0_CMP)) > /* do nothing */ ; > } else { > int c1, c2; but, but. Didn't this get fixed by ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.23-rc2/2.6.23-rc2-mm1/broken-out/fix-hpet-init-race.patch ? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/