On Tue, Dec 13, 2016 at 02:56:14PM -0600, Bjorn Helgaas wrote:
> On Fri, Oct 28, 2016 at 06:58:15PM -0400, Keith Busch wrote:
> > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > index 0e49f70..2115d19 100644
> > --- a/include/linux/pci.h
> > +++ b/include/linux/pci.h
> > @@ -341,6 +341,7 @@ struct pci_dev {
> > unsigned int multifunction:1;/* Part of multi-function device */
> > /* keep track of device state */
> > unsigned int is_added:1;
> > + unsigned int is_removed:1; /* device was surprise removed */
> > unsigned int is_busmaster:1; /* device is busmaster */
> > unsigned int no_msi:1; /* device may not use msi */
> > unsigned int no_64bit_msi:1; /* device may only use 32-bit MSIs */
> > @@ -417,6 +418,12 @@ static inline int pci_channel_offline(struct pci_dev *pdev)
> > return (pdev->error_state != pci_channel_io_normal);
> > }
> >
> > +static inline int pci_set_removed(struct pci_dev *pdev, void *unused)
> > +{
> > + pdev->is_removed = 1;
>
> This makes me slightly worried because this is a bitfield and there's
> no locking. A concurrent write to some nearby field can corrupt
> things. It doesn't look *likely*, but it's a lot of work to be
> convinced that this is completely safe, especially since the writer is
> running on behalf of the bridge, and the target is a child of the
> bridge.
>
> The USB HCD_FLAG_DEAD and HCD_FLAG_HW_ACCESSIBLE flags are somewhat
> similar. Maybe we can leverage some of that design?
A bit field with atomic accessors sounds good to me. Do you want to
see all the struct pci_dev bit flags converted to that model? If so,
I can send you a prep patch that does that first.
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