Re: [linus:master] [tpm, tpm_tis] e644b2f498: RIP:acpi_safe_halt

[Lukas Wunner]

On Thu, May 11, 2023 at 01:22:19PM +0200, Lino Sanfilippo wrote:
> Since beside the one reported by Peter Zijlstra 
> (https://lore.kernel.org/linux-integrity/CSJ0AD1CFYQP.T6T68M6ZVK49@suppilovahvero/T/#t)
> we have another interrupt storm here, it is probably the best to handle those in general
> and to disable interrupts in this case to fall back to polling (this is also what Jerry
> suggested in the thread above).
> 
> I will try to provide a patch for this.

In tpm_tis_probe_irq_single(), after you've requested the irq,
you could convert it to a struct irq_desc (via irq_to_desc()
from <linux/irqnr.h>) and cache that pointer in priv.

Then in tis_int_handler(), you could access the irqs_unhandled
member of struct irq_desc (from <linux/irqdesc.h>) and check
if it exceeds, say, 5000.

If it does, schedule a work_struct which calls disable_interrupts().
You can't call that from the IRQ handler because devm_free_irq()
waits for the IRQ handler to finish, so you'd deadlock.  You *can*
of course clear the TPM_GLOBAL_INT_ENABLE bit from the IRQ handler,
though it's unclear to me if that's sufficient to quiesce the
interrupt line.

By reusing the genirq subsystem's irqs_unhandled infrastructure,
you avoid having to reimplement all of that.

Thanks,

Lukas