linux-kernel - Re: [linus:master] [tpm, tpm_tis] e644b2f498: RIP:acpi_safe

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Message-ID: <1a8ecf90-80a4-9aac-95e1-9ce0c4e09ba5@kunbus.com>
Date:   Thu, 11 May 2023 16:22:02 +0200
From:   Lino Sanfilippo <l.sanfilippo@...bus.com>
To:     Lukas Wunner <lukas@...ner.de>
Cc:     Jarkko Sakkinen <jarkko@...nel.org>, oe-lkp@...ts.linux.dev,
        lkp@...el.com, linux-kernel@...r.kernel.org,
        Michael Niewöhner <linux@...ewoehner.de>,
        linux-integrity@...r.kernel.org,
        Philipp Rosenberger <p.rosenberger@...bus.com>,
        jsnitsel@...hat.com, peterz@...radead.org
Subject: Re: [linus:master] [tpm, tpm_tis] e644b2f498: RIP:acpi_safe_halt


Hi Lukas,

On 11.05.23 16:16, Lukas Wunner wrote:
> ATTENTION: This e-mail is from an external sender. Please check attachments and links before opening e.g. with mouseover.
> 
> 
> 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