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    SubjectRe: [PATCH RFC 0/8] jump-label: allow early jump_label_enable()
    On 09/29/2011 05:52 PM, Steven Rostedt wrote:
    > On Thu, 2011-09-29 at 16:26 -0700, Jeremy Fitzhardinge wrote:
    >> From: Jeremy Fitzhardinge <>
    >> One big question which arises is whether the _early() function is
    >> necessary at all. All the stop_machine/mutex/etc stuff that
    >> arch_jump_label_transform() ends up doing is redundant pre-SMP, but it
    >> shouldn't hurt. Maybe we can just drop the _early function? It works
    >> on x86, at least, because jump_label_enable() works, which uses the full
    >> form. And dropping it would reduce this to a very much smaller series.
    > It does slow down the boot process, which is not a good thing when
    > everyone is pushing for the fastest restarts.

    Would it really though? stop_machine() doesn't do very much when there
    are no other cpus.

    Not that I measured or anything, but there was no obvious big lag at boot.

    > What we should probably do is have a global read_mostly variable called,
    > smp_activated or something, then things that can be called before and
    > after can read this variable to determine if it can skip certain
    > protections.

    Could do that if it turns out to be a problem.

    > While we're at it, perhaps we could add a memory_initialized for things
    > like tracers that want to trace early but need to wait till it can
    > allocate buffers. If we had this flag, it could instead do an early
    > memory init to create the buffers.

    That seems orthogonal to the jump_label changes.


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