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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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