Re: [PATCH v2 2/2] PCI: pciehp: Prevent deadlock on disconnect

[Mika Westerberg]

On Mon, Sep 23, 2019 at 11:12:42AM +0300, Mika Westerberg wrote:
> Regarding suggestion of unbinding PCI drivers without
> pci_lock_rescan_remove() hold, I haven't looked it too closely but I
> think we need to take that lock anyway because when we are unbinding a
> hotplug driver it is supposed to remove the hierarchy below touching the
> shared structures, possibly concurrently. Unfortunately there is no
> documentation what data pci_lock_rescan_remove() actually protects so
> first one needs to understand that. I think one way to clean up this is
> to use finer grained locking (with documented lock ordering) for PCI bus
> structures that can be accessed simultaneusly by different threads. But
> that is not a simple task.

Now that I looked more closely, I realized it actually is not supposed
to remove the hierarchy below so indeed it might be possible to do that
without taking pci_lock_rescan_remove().