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SubjectRe: [PATCH V2] PCI: AER: fix deadlock in do_recovery
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?

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