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    SubjectRe: [patch 1/9] Fix HPET init race
    On Thu, 01 Feb 2007 10:59:53 +0100 jbohac@suse.cz wrote:

    > Fix a race in the initialization of HPET, which might result in a
    > 5 minute lockup on boot.
    >

    What race? Please always describe bugs when fixing them.

    >
    > Index: linux-2.6.20-rc5/arch/x86_64/kernel/apic.c
    > ===================================================================
    > --- linux-2.6.20-rc5.orig/arch/x86_64/kernel/apic.c
    > +++ linux-2.6.20-rc5/arch/x86_64/kernel/apic.c
    > @@ -764,10 +767,12 @@ static void setup_APIC_timer(unsigned in
    >
    > /* wait for irq slice */
    > if (vxtime.hpet_address && hpet_use_timer) {
    > - int trigger = hpet_readl(HPET_T0_CMP);
    > - while (hpet_readl(HPET_COUNTER) >= trigger)
    > - /* do nothing */ ;
    > - while (hpet_readl(HPET_COUNTER) < trigger)
    > + int trigger;
    > + do
    > + trigger = hpet_readl(HPET_T0_CMP);
    > + while (hpet_readl(HPET_COUNTER) >= trigger);
    > +

    Is this signedness-safe and wraparound-safe? It might be better to make
    `trigger' unsigned and do

    while (hpet_readl(HPET_COUNTER) - trigger >= 0)

    > + while (hpet_readl(HPET_COUNTER) < trigger)
    > /* do nothing */ ;

    ditto.
    -
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