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    SubjectRe: [PATCH] netpoll: Fix carrier detection for drivers that are using phylib
    On Wed, 2009-07-08 at 17:01 -0700, Linus Torvalds wrote:
    > On Thu, 9 Jul 2009, Anton Vorontsov wrote:
    > >
    > > The netpoll code is using msleep() just a few lines below cond_resched(),
    > > so we won't make things worse. ;-)
    > Yeah. That function is definitely sleeping. It does things like
    > kmalloc(GFP_KERNEL), rtnl_lock() and synchronize_rcu() etc too, so an
    > added msleep() is the least of our problems.
    > Afaik, it's called from a bog-standard "module_init()", which happens late
    > enough that everything works.
    > In fact, I wonder if we should set SYSTEM_RUNNING much earlier - _before_
    > doing the whole "do_initcalls()".

    Well there are two ways of consistently defining SYSTEM_RUNNING:

    a) define it with reference to the well-understood notion of booting vs
    running and don't switch it until handing off to init

    b) define it with reference to its usage by an arbitrary user like

    In the latter case, we obviously need to move it to the earliest point
    that scheduling is possible. But there are a number of things like

    that assume the definition is actually (a). We're currently within a
    couple lines of a strict definition of (a) already, so I actually think
    cond_resched() is just wrong (and we already know it broke a
    previously-working user). It should perhaps be using another private
    flag that gets set as soon as scheduling is up and running.

    But I'd actually go further and say that it's unfortunate to be checking
    extra flags in such an important inline, especially since the check is
    false for all but the first couple seconds of run time. Seems like we
    could avoid adding an extra check by artificially elevating the preempt
    count in early boot (or at compile time) then dropping it when
    scheduling becomes available.

    -- : development and support for Mercurial and Linux

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