* Ingo Molnar <mi...@kernel.org> wrote:
>
> * Anton Blanchard <an...@samba.org> wrote:
>
> > +static arch_spinlock_t die_lock = __ARCH_SPIN_LOCK_UNLOCKED;
> > +static int die_owner = -1;
> > +static unsigned int die_nest_count;
> > +
> > +unsigned long __die_spin_lock_irqsave(void)
> > +{
> > + unsigned long flags;
> > + int cpu;
> > +
> > + /* racy, but better than risking deadlock. */
> > + raw_local_irq_save(flags);
> > +
> > + cpu = smp_processor_id();
> > + if (!arch_spin_trylock(&die_lock)) {
> > + if (cpu != die_owner)
> > + arch_spin_lock(&die_lock);
>
> So why not trylock and time out here after a few seconds,
> instead of indefinitely supressing some potentially vital
> output due to some other CPU crashing/locking with the lock
> held?
[...]
> If we fix the deadlock potential, and get a true global
> ordering of various oopses/warnings as they triggered (or
> at least timestamping them), [...]
If we had a global 'trouble counter' we could use that to
refine the spin-looping timeout: instead of using a pure
timeout of a few seconds, we could say 'a timeout of a few
seconds while the counter does not increase'.
I.e. only override the locking/ordering if the owner CPU
does not seem to be able to make progress with printing the
oops/warning.
Thanks,
Ingo
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