Re: [PATCH V2] PCI: AER: fix deadlock in do_recovery

[Govindarajulu Varadarajan]

On Sun, 1 Oct 2017, Christoph Hellwig wrote:

> > +struct aer_device_list {
> > +	struct device *dev;
> > +	struct hlist_node node;
> > +};
> > +
> >  extern struct bus_type pcie_port_bus_type;
> >  void aer_isr(struct work_struct *work);
> >  void aer_print_error(struct pci_dev *dev, struct aer_err_info *info);
> > diff --git a/drivers/pci/pcie/aer/aerdrv_core.c b/drivers/pci/pcie/aer/aerdrv_core.c
> > index 890efcc574cb..d524f2c2c288 100644
> > --- a/drivers/pci/pcie/aer/aerdrv_core.c
> > +++ b/drivers/pci/pcie/aer/aerdrv_core.c
> > @@ -346,6 +346,47 @@ static int report_resume(struct pci_dev *dev, void *data)
> >  	return 0;
> >  }
> >
> > +int aer_get_pci_dev(struct pci_dev *pdev, void *data)
> > +{
> > +	struct hlist_head *hhead = (struct hlist_head *)data;
> > +	struct device *dev = &pdev->dev;
> > +	struct aer_device_list *entry;
> > +
> > +	entry = kmalloc(sizeof(*entry), GFP_KERNEL);
> > +	if (!entry)
> > +		/* continue with other devices, lets not return error */
> > +		return 0;
> > +
> > +	entry->dev = get_device(dev);
> > +	hlist_add_head(&entry->node, hhead);
> > +
> > +	return 0;
>
> Can we just embedded the list_head in the pci_dev?  Or is there a way
> we can have multiple chains like this pending at the same time?

I would avoid increasing the size of pci_dev. The list_head would be empty after
we call aer_pci_walk_bus(). We already have pci_bus *subordinate to link all the
'device's. Making list_head available to others would require a lock. I would
avoid that.

> > +static void aer_pci_walk_bus(struct pci_bus *top,
> > +			     int (*cb)(struct pci_dev *, void *),
> > +			     struct aer_broadcast_data *result)
> > +{
> > +	HLIST_HEAD(dev_hlist);
> > +	struct hlist_node *tmp;
> > +	struct aer_device_list *entry;
>
> Do we want to offer this as generic PCIe functionality?  If not we can
> probably hardcode the callback and callback data to simplify this a lot.

I could not find any other code which aquires device_lock in pci_walk_bus cb
function. Can you tell me how we can hardcore callback and callback data here?