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    SubjectRe: [2.6 patch] i386: always use 4k/4k stacks
    Am Sonntag 18 Dezember 2005 12:21 schrieb Arjan van de Ven:

    > the kernel has a stack overflow detector, which checks at irq entry time
    > if the stack is "rather high" (7kb into the stack on a 8kb stack, 3.5kb
    > on a 4k stack). When this warning hits there's still runway left (like
    > 12.5 percent), but lets say the end becomes in sight. If the stack usage
    > would be really tight, this "early warning" detector would be hitting a
    > lot of people, right?

    Wrong. The probability that an interrupt happens just during the codepath with
    highest stack usage is very small. Anyway CONFIG_DEBUG_STACKOVERFLOW is not
    enabled in i386 defconfig. Don't know about vendor kernel kernels

    I thought more about filling the stack with some arbitrary value on thread
    startup and checking how much has been overwritten on a regular basis. Part
    of it is alreay there, hidden unter CONFIG_DEBUG_STACK_USAGE. The
    verification should just happen timer-controlled, not only on sysrq-whatever.

    > (and the "safety net" is a bit of misnomer, since it's not really safe,
    > just "statistically different" if the shit hits the fan)

    If you can't even guarantee that 8k (or 6k) is enough, how can you vote for 4k
    then ;-) Just a little provocation, I don't plan getting too involved into
    this dicussion, hell, this is just about a ridiculously small amount of self
    contained #ifdef'd code ;-)

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