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    SubjectRe: [PATCH 1/1] x86: fix text_poke

    * Linus Torvalds <torvalds@linux-foundation.org> wrote:

    > No. That whole code sequence is total and utter crap. It needs to be
    > rewritten.
    >
    > It first does a BUG_ON() if it's not naturally aligned (because that
    > wouldn't be atomic), and then it has code for page crossing! What a
    > TOTAL PIECE OF SH*T!
    >
    > Hint:
    > - if it's naturally aligned, it couldn't be page crossing ANYWAY
    > - and if it was a page-crosser, it sure as hell couldn't be atomic!
    >
    > The code is just crap, crap, crap. It needs to be rewritten from
    > scratch. I'll have a patch soonish.

    yeah :(

    it seems that this code only worked because text_poke_early() [which can
    take arbitrary length and alignment] does most of the patching, it is
    the real code-patching machinery that is used during early bootup - and
    that's not used later on.

    text_poke() itself only applies/unapplies the LOCK prefix - a single
    byte. We shouldnt be doing that at all: the cost of LOCK is
    insignificant (a few cycles) and most systems are SMP anyway.

    any other type of code patching should use stop_machine_run(), where
    every CPU is stopped with irqs disabled.

    Ingo


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