Re: [PATCH] tpm,tpm_tis: Avoid warning splat at shutdown

[Lino Sanfilippo <l.sanfilippo@kunbus.com>]

On 01.02.24 17:40, Elliott, Robert (Servers) wrote:
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> 
>> From: Lino Sanfilippo <l.sanfilippo@kunbus.com>
>> Sent: Thursday, February 1, 2024 5:37 AM
>> Subject: [PATCH] tpm,tpm_tis: Avoid warning splat at shutdown
>>
>> If interrupts are not activated the work struct 'free_irq_work' is not
>> initialized. This results in a warning splat at module shutdown.
>>
>> Fix this by always initializing the work regardless of whether interrupts
>> are activated or not.
> 
> That's using flush_work(), which just waits for one to complete. Is there
> any case where multiple work entries could be queued, and cancel_work_sync()
> would be necessary?
> 

No. There is only one work struct (namely free_irq_work) and it can only be
queued once at a time (note that schedule_work() does not queue the same work
again if it is already queued).   

> tpm_tis_probe_irq() has a loop calling tpm_tis_probe_irq_single()
> for 3 to 15. Could each of those could trigger an interrupt storm and
> call tpm_tis_revert_interrupts(), which calls schedule_work()?
> 
> 

The iteration stops as soon as there is an interrupt found that "works" (i.e.
as soon as one interrupt fires, see the "irq test" in tpm_tis_send()). If this
irq starts a storm it is handled by the implemented irq storm handling and
deactivated. No other interrupts are activated afterwards. So no,
I do not see that multiple interrupt storms are possible at the same time.

Regards,
Lino