From: John Garry <john.garry@huawei.com>
To: Marc Zyngier <maz@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
<gregkh@linuxfoundation.org>, <rafael@kernel.org>,
<martin.petersen@oracle.com>, <jejb@linux.ibm.com>,
<linuxarm@huawei.com>, <linux-scsi@vger.kernel.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 1/3] genirq/affinity: Add irq_update_affinity_desc()
Date: Mon, 23 Nov 2020 12:54:45 +0000 [thread overview]
Message-ID: <0edc9a11-0b92-537f-1790-6b4b6de4900d@huawei.com> (raw)
In-Reply-To: <87sg91ik9e.wl-maz@kernel.org>
Hi Marc,
>>> Right, but if the driver is removed then the interrupts should be
>>> deallocated, right?
>>>
>>
>> When removing the driver we just call free_irq(), which removes the
>> handler and disables the interrupt.
>>
>> But about the irq_desc, this is created when the mapping is created in
>> irq_create_fwspec_mapping(), and I don't see this being torn down in
>> the driver removal, so persistent in that regard.
>
> If the irq_descs are created via the platform_get_irq() calls in
> platform_get_irqs_affinity(), I'd expect some equivalent helper to
> tear things down as a result, calling irq_dispose_mapping() behind the
> scenes.
>
So this looks lacking in the kernel AFAICS...
So is there a reason for which irq dispose mapping is not a requirement
for drivers when finished with the irq? because of shared interrupts?
>> So for pci msi I can see that we free the irq_desc in
>> pci_disable_msi() -> free_msi_irqs() -> msi_domain_free_irqs() ...
>>
>> So what I am missing here?
>
> I'm not sure the paths are strictly equivalent. On the PCI side, we
> can have something that completely driver agnostic, as it is all
> architectural. In your case, only the endpoint driver knows about what
> happens, and needs to free things accordingly.
>
> Finally, there is the issue in your driver that everything is
> requested using devm_request_irq, which cannot play nicely with an
> explicit irq_desc teardown. You'll probably need to provide the
> equivalent devm helpers for your driver to safely be taken down.
>
Yeah, so since we use the devm irq request method, we also need a devm
dispose release method as we can't dispose the irq mapping in the
remove() method, prior to the irq_free() in the later devm release method.
But it looks like there is more to it than that, which I'm worried is
far from non-trivial. For example, just calling irq_dispose_mapping()
for removal and then plaform_get_irq()->acpi_get_irq() second time fails
as it looks like more tidy-up is needed for removal...
Cheers,
John
next prev parent reply other threads:[~2020-11-23 12:59 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-28 12:33 [PATCH v2 0/3] Support managed interrupts for platform devices John Garry
2020-10-28 12:33 ` [PATCH v2 1/3] genirq/affinity: Add irq_update_affinity_desc() John Garry
2020-10-28 18:22 ` Thomas Gleixner
2020-11-02 17:32 ` John Garry
2020-11-02 20:35 ` Thomas Gleixner
2020-11-17 21:28 ` Thomas Gleixner
2020-11-18 11:34 ` John Garry
2020-11-18 20:38 ` Thomas Gleixner
2020-11-19 9:31 ` John Garry
2020-11-19 18:09 ` Thomas Gleixner
2020-11-19 19:56 ` John Garry
2020-11-19 21:03 ` Thomas Gleixner
2020-11-20 11:52 ` John Garry
2020-11-22 13:38 ` Marc Zyngier
2020-11-23 12:54 ` John Garry [this message]
2020-11-23 13:26 ` Marc Zyngier
2020-11-23 15:45 ` John Garry
2020-11-24 16:51 ` Marc Zyngier
2020-11-24 17:38 ` John Garry
2020-11-25 18:35 ` Marc Zyngier
2020-11-26 10:47 ` John Garry
2020-11-26 11:08 ` Marc Zyngier
2020-11-26 11:29 ` John Garry
2020-11-26 16:52 ` John Garry
2020-11-27 9:57 ` Marc Zyngier
2020-11-27 12:45 ` John Garry
2020-11-27 12:49 ` Marc Zyngier
2020-10-28 12:33 ` [PATCH v2 2/3] Driver core: platform: Add platform_get_irqs_affinity() John Garry
2020-10-28 12:33 ` [PATCH v2 3/3] scsi: hisi_sas: Expose HW queues for v2 hw John Garry
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