linux-kernel - Re: [PATCH v2 1/3] genirq/affinity: Add irq_update_affinity

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Date:   Fri, 20 Nov 2020 11:52:09 +0000
From:   John Garry <john.garry@...wei.com>
To:     Thomas Gleixner <tglx@...utronix.de>, <gregkh@...uxfoundation.org>,
        <rafael@...nel.org>, <martin.petersen@...cle.com>,
        <jejb@...ux.ibm.com>
CC:     <linuxarm@...wei.com>, <linux-scsi@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <maz@...nel.org>
Subject: Re: [PATCH v2 1/3] genirq/affinity: Add irq_update_affinity_desc()

Hi Thomas,

>> Just mentioning a couple of things here, which could be a clue to what
>> is going on:
>> - the device is behind mbigen secondary irq controller
>> - the flow in the LLDD is to allocate all 128 interrupts during probe,
>> but we only register handlers for a subset with device managed API
> 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.

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?

Thanks,
John