Re: [PATCH v3] switchtec: Fix stdev_release crash after suprise device loss.

[Bjorn Helgaas <helgaas@kernel.org>]

On Tue, Nov 21, 2023 at 03:58:22PM -0800, Daniel Stodden wrote:
> > On Nov 21, 2023, at 10:40 AM, Bjorn Helgaas <helgaas@kernel.org> wrote:
> > On Tue, Nov 21, 2023 at 10:23:51AM -0800, Daniel Stodden wrote:
> >>> On Nov 20, 2023, at 1:25 PM, Bjorn Helgaas <helgaas@kernel.org> wrote:
> >>> On Mon, Nov 13, 2023 at 01:21:50PM -0800, Daniel Stodden wrote:
> >>>> A pci device hot removal may occur while stdev->cdev is held open. The
> >>>> call to stdev_release is then delivered during close or exit, at a
> >>>> point way past switchtec_pci_remove. Otherwise the last ref would
> >>>> vanish with the trailing put_device, just before return.
> >>>> 
> >>>> At that later point in time, the device layer has alreay removed
> >>>> stdev->mrpc_mmio map. Also, the stdev->pdev reference was not a
> >>> 
> >>> I guess this should say the "stdev->mmio_mrpc" (not "mrpc_mmio")?
> >> 
> >> Eww. My fault. Could you still correct that?
> > 
> > Yep, I speculatively made that change already, so thanks for
> > confirming it :)
> > 
> > https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git/commit/?h=switchtec&id=f9724598e29d
> 
> Thanks. And sorry for what’s next. 
> 
> Look what I just found in my internal review inbox.
> 
> Signed-off/Reviewed-by: dima@arista.com

Happy to add that, no problem, but:

  - "Signed-off-by" has a specific meaning about either being involved
    in the creation of the patch or being part of the chain of
    transmitting the patch, see
    https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?id=v6.6#n396
    Since I got the patch directly from you, adding a signed-off-by
    from dima@ would mean he created part of the patch.

  - I don't think it makes sense to include both Signed-off-by and
    Reviewed-by from the same person, since the point of Reviewed-by
    is to get review by somebody other than the author.

  - dima@ should include a name as well as the email address (I assume
    "Dmitry Safonov <dima@arista.com>")

So if you want to use a Signed-off-by from Dmitry, please post a v4
including that (ideally starting from the commit above because I
silently fixed a couple other typos (although I missed the
put_device() thing)).

If you prefer a Dmitry's Reviewed-by, no need to post a v4.  The best
thing would be for Dmitry to respond with the Reviewed-by on the
mailing list.  Some people do collect reviews internally, but I prefer
to get them directly from the reviewer.

Bjorn