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    SubjectRe: [patch 3/5] [PATCH 3/5] x86: Run Intel ucode-updates via workqueue.
    2008/8/6 Arjan van de Ven <arjan@infradead.org>:
    > On Wed, 6 Aug 2008 17:21:20 +0200
    > Peter Oruba <peter.oruba@amd.com> wrote:
    >
    > [ no description or reason ]
    >
    > Why is this?

    More details are available here.

    I've also suggested to do ucode-updates as early as possible from
    start_secondary() (or whatever low-level code).

    The second patch (do via workqueue) was just a proof-of-concept (to
    show that it does fix a crash).

    >
    > I'm not very happy about this.. it means practically that this stuff
    > *has* to run late. Probably later than we want to.

    Currently, it runs from cpu-hotplug-notifier(CPU_ONLINE, ...)
    [ and crashes with .26+ due to a reason you may find via the
    aforementioned link ] - by this moment, at least kernel threads may
    running on this cpu -- so it's not that early.

    > (Like.. we may want to redo the microcode during resume.. which is
    > not a schedulable context)

    I'm not sure what's "schedulable context" here terms but the existing
    code makes use of set_cpus_allowed_ptr() which means a caller expects
    to be able to be migrated onto a target cpu and do ucode-update while
    running on it.

    Moreover, the way set_cpus_allowed_ptr() is used there seems to be
    race wrt. sched_setaffinity().


    --
    Best regards,
    Dmitry Adamushko


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