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Re: [patch V2 02/31] genirq/msi: Add mutex for MSI list protection
- To: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
- From: Jason Gunthorpe <jgg@xxxxxxxxxx>
- Date: Wed, 8 Dec 2021 20:47:02 -0400
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- Cc: LKML <linux-kernel@xxxxxxxxxxxxxxx>, Bjorn Helgaas <helgaas@xxxxxxxxxx>, Marc Zygnier <maz@xxxxxxxxxx>, Alex Williamson <alex.williamson@xxxxxxxxxx>, Kevin Tian <kevin.tian@xxxxxxxxx>, Megha Dey <megha.dey@xxxxxxxxx>, Ashok Raj <ashok.raj@xxxxxxxxx>, linux-pci@xxxxxxxxxxxxxxx, Cedric Le Goater <clg@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, Juergen Gross <jgross@xxxxxxxx>, Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>, Niklas Schnelle <schnelle@xxxxxxxxxxxxx>, linux-s390@xxxxxxxxxxxxxxx, Heiko Carstens <hca@xxxxxxxxxxxxx>, Christian Borntraeger <borntraeger@xxxxxxxxxx>, Logan Gunthorpe <logang@xxxxxxxxxxxx>, Jon Mason <jdmason@xxxxxxxx>, Dave Jiang <dave.jiang@xxxxxxxxx>, Allen Hubbe <allenbh@xxxxxxxxx>, linux-ntb@xxxxxxxxxxxxxxxx
- Delivery-date: Thu, 09 Dec 2021 00:47:22 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On Mon, Dec 06, 2021 at 11:51:05PM +0100, Thomas Gleixner wrote:
> +++ b/kernel/irq/msi.c
> @@ -127,12 +127,37 @@ int msi_setup_device_data(struct device
> return -ENOMEM;
>
> INIT_LIST_HEAD(&md->list);
> + mutex_init(&md->mutex);
> dev->msi.data = md;
> devres_add(dev, md);
> return 0;
> }
>
> /**
> + * msi_lock_descs - Lock the MSI descriptor storage of a device
> + * @dev: Device to operate on
> + */
> +void msi_lock_descs(struct device *dev)
> +{
> + if (WARN_ON_ONCE(!dev->msi.data))
> + return;
Is this useful? Other places that call msi_lock_descs will continue on and deref
null dev->msi anyhow - is the dump from the WARN_ON that much better
than the oops from the null deref here:
> + mutex_lock(&dev->msi.data->mutex);
?
Honestly, still a bit unclear on what the community consensus is for
using WARN_ON.
Jason
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