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    SubjectRe: [PATCH][BUG] Badness in smp_call_function at arch/i386/kernel/smp.c:552
    Zwane Mwaikambo <zwane@holomorphy.com> wrote:
    >
    > > Well, sort-of.
    > >
    > > If __handle_sysrq was really a normal IRQ handler then the correct thing to
    > > do here is to replace spin_lock_irqsave() with spin_lock(). But
    > > __handle_sysrq() can also be called via /proc/sysrq-trigger and via the
    > > handlers of multiple interrupt sources. So we're stuck with using
    > > spin_lock_irqsave().
    > >
    > > However enabling interrupts as you've done menas that theoretically we
    > > could deadlock on sysrq_key_table_lock if another sysrq happens at the
    > > wrong time.
    > >
    > > Which deadlock opportunity would you prefer? ;)
    >
    > Agreed, there is actually a higher chance of the smp_call_function
    > deadlock occuring since the __handle_sysrq one relies on another sysrq
    > event occuring via a different IRQ line interrupt handler, so
    > we would have to do sysrq via serial and then sysrq via keyboard to cause
    > the deadlock. Perhaps just make it a spin_trylock?

    Well yeah, but it's so much fuss for such a silly problem.

    How about a local_irq_enable() in sysrq_handle_reboot()?
    -
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