linux-kernel - Re: [patch 07/32] genirq/msi: Count the allocated MSI descriptors

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Message-ID: <87o865flot.ffs@tglx>
Date:   Sat, 27 Nov 2021 20:22:26 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Marc Zygnier <maz@...nel.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Megha Dey <megha.dey@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, linux-pci@...r.kernel.org,
        linux-s390@...r.kernel.org, Heiko Carstens <hca@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Jon Mason <jdmason@...zu.us>,
        Dave Jiang <dave.jiang@...el.com>,
        Allen Hubbe <allenbh@...il.com>, linux-ntb@...glegroups.com
Subject: Re: [patch 07/32] genirq/msi: Count the allocated MSI descriptors

On Sat, Nov 27 2021 at 13:19, Greg Kroah-Hartman wrote:
> On Sat, Nov 27, 2021 at 02:22:38AM +0100, Thomas Gleixner wrote:
>> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
>
> No changelog?

Bah. This one should not be there at all.

> Anyway, why do we care about the number of decriptors?
>> +/**
>> + * msi_device_num_descs - Query the number of allocated MSI descriptors of a device
>> + * @dev:	The device to read from
>> + *
>> + * Note: This is a lockless snapshot of msi_device_data::num_descs
>> + *
>> + * Returns the number of MSI descriptors which are allocated for @dev
>> + */
>> +unsigned int msi_device_num_descs(struct device *dev)
>> +{
>> +	if (dev->msi.data)
>> +		return dev->msi.data->num_descs;
>
> As this number can change after it is read, what will callers do with
> it?

I wanted to get rid of this, but then forgot. Getting old.

Thanks,

        tglx