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

[Lino Sanfilippo]

Hi Lukas,

On 11.05.23 16:16, Lukas Wunner wrote:
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> 
> 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.

This is the solution I am currently working on, but thanks for confirming that 
I am on the right track with this :)

> 
> 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.
> 

Will try this, thx.

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

Agreed.

Regards,
Lino

> Thanks,
> 
> Lukas