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    SubjectRe: [patch] shaper fix for timer SMP races
    Andrea Arcangeli <andrea@e-mind.com> wrote:
    >I developed a new patch that I sent to Alex now for testing.
    > --- shaper.c 1999/01/18 01:28:09 1.1.1.1
    > +++ linux/drivers/net/shaper.c 1999/02/16 13:25:36
    > [...]
    > @@ -405,7 +394,9 @@
    > {
    > struct shaper *shaper=dev->priv;
    > shaper_flush(shaper);
    > + start_bh_atomic();
    > del_timer(&shaper->timer);
    > + end_bh_atomic();
    > MOD_DEC_USE_COUNT;
    > return 0;
    > }

    Isn't that part of the patch overkill?

    As I understand things, del_timer() must acquire the timerlist_lock
    spinlock to modify the timer list. I guess that all other code
    (including the code in bottom half handlers) that want to modify the
    timer list do the same.

    So why do we need to use [start|end]_bh_atomic() to guarantee that no
    BH on any CPU will execute while we modify the timer list?

    Best regards,
    --
    Regis "HPReg" Duchesne - InfoVista US technical support
    www http://www.InfoVista.com/
    (O o) I use Linux (1135 KB/s over 10Mb/s ethernet)
    --.oOO--(_)--OOo.----------------------------------------------------
    If cryptography is outlawed, only outlaws will have cryptography


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