Re: [PATCH] PCI: Fix AB-BA deadlock between remove and SR-IOV sysfs

[Benjamin Block]

On Mon, Jul 06, 2026 at 10:16:36AM +0200, Niklas Schnelle wrote:
> On Sun, 2026-07-05 at 23:24 +0800, Guangshuo Li wrote:
> > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> > index 5ec0b245a69b..5eae72508129 100644
> > --- a/drivers/pci/pci-sysfs.c
> > +++ b/drivers/pci/pci-sysfs.c
> > @@ -519,8 +519,35 @@ static ssize_t remove_store(struct device *dev, struct device_attribute *attr,
> >  	if (kstrtoul(buf, 0, &val) < 0)
> >  		return -EINVAL;
> >  
> > -	if (val && device_remove_file_self(dev, attr))
> > +	if (val && device_remove_file_self(dev, attr)) {
> > +		/*
> > +		 * Mark the device as dead so that no new driver can bind
> > +		 * between the unbind and the removal below. Once the dead
> > +		 * flag is set, the device core will refuse any new driver
> > +		 * probe.
> > +		 */
> > +		device_lock(dev);
> > +		kill_device(dev);
> > +		device_unlock(dev);
> > +
> > +		/*
> > +		 * Unbind the driver before removing the device to avoid an
> > +		 * AB-BA deadlock between device_lock() and
> > +		 * pci_rescan_remove_lock. Without this, remove_store() takes
> > +		 * pci_rescan_remove_lock first via
> > +		 * pci_stop_and_remove_bus_device_locked(), then takes
> > +		 * device_lock() during driver release, while a concurrent
> > +		 * sriov_numvfs_store() takes device_lock() first and then
> > +		 * pci_rescan_remove_lock via SR-IOV VF removal.
> > +		 *
> > +		 * By unbinding first, the driver's .remove() callback,
> > +		 * including any SR-IOV VF cleanup, completes before
> > +		 * pci_rescan_remove_lock is acquired.
> > +		 */
> > +		device_release_driver(dev);
> >  		pci_stop_and_remove_bus_device_locked(to_pci_dev(dev));
> > +	}
> > +
> >  	return count;
> >  }
> >  static DEVICE_ATTR_IGNORE_LOCKDEP(remove, 0220, NULL,
> 
> This seems to be a complete duplicate of Ionut Nechita's patch[0] from
> April. The comments are close enough, but not identical, that I don't
> think this can really have been created independently.

Yep, +1.
This is not helpful. We still want the original patchset included (I sent a
ping a few minutes ago), but then in its complete form with the proper
authors.

-- 
Best Regards, Benjamin Block        /        Linux on IBM Z Kernel Development
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