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    SubjectRe: Linux 2.6.24-rc5 x86 architecture no longer Oopses...

    * Andrew Morton <akpm@linux-foundation.org> wrote:

    > > + raw_local_irq_save(flags);
    > > __raw_spin_lock(&die.lock);
    > > - raw_local_save_flags(flags);
    > > die.lock_owner = smp_processor_id();
    > > die.lock_owner_depth = 0;
    > > bust_spinlocks(1);
    > > - }
    > > - else
    > > - raw_local_save_flags(flags);
    > > + } else
    > > + raw_local_irq_save(flags);
    > >
    > > if (++die.lock_owner_depth < 3) {
    > > unsigned long esp;
    >
    > Looks sane.
    >
    > I suppose there's some reason why we can't just use
    > spin_lock_irqsave(). But that reason was either so obvious or so
    > unimportant that a comment was not needed. Sigh.

    bug was introduced via:

    commit 39743c9ef717fd4f2b5583f010115c5f2482b8ae
    Author: Andi Kleen <ak@suse.de>
    Date: Fri Oct 19 20:35:03 2007 +0200

    x86: use raw locks during oopses

    - spin_lock_irqsave(&die.lock, flags);
    + __raw_spin_lock(&die.lock);
    + raw_local_save_flags(flags);

    that is not a correct open-coding of spin_lock_irqsave(): both the
    ordering is wrong (irqs should be disabled _first_), and the wrong
    flags-saving API was used.

    so this is a post-2.6.23 regression and the fix is (now) obvious.

    Ingo


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