Re: [PATCH AUTOSEL 5.5 094/542] s390/pci: Fix possible deadlock in recover_store()

[Sasha Levin]

On Mon, Feb 17, 2020 at 10:31:56AM +0100, Niklas Schnelle wrote:
> On Fri, Feb 14, 2020 at 10:41:26AM -0500, Sasha Levin wrote:
> > From: Niklas Schnelle <schnelle@xxxxxxxxxxxxx>
> >
> > [ Upstream commit 576c75e36c689bec6a940e807bae27291ab0c0de ]
> >
> > With zpci_disable() working, lockdep detected a potential deadlock
> > (lockdep output at the end).
> >
> > The deadlock is between recovering a PCI function via the
> >
> > /sys/bus/pci/devices/<dev>/recover
> >
> > attribute vs powering it off via
> >
> > /sys/bus/pci/slots/<slot>/power.
> >
> > The fix is analogous to the changes in commit 0ee223b2e1f6 ("scsi: core:
> > Avoid that SCSI device removal through sysfs triggers a deadlock")
> > that fixed a potential deadlock on removing a SCSI device via sysfs.
> [ ... snip ... ]
>
> While technically useful on its own this commit really should go together with
> the following upstream commit:
>
> 17cdec960cf776b20b1fb08c622221babe591d51
> ("s390/pci: Recover handle in clp_set_pci_fn()")
>
> While the problem fixed here is independent,  writing to the power/recover
> attributes will often fail due to an inconsistent function handle without the
> second commit.
> In particular without it a PCI function in the error state can not be
> recovered or powered off.
>
> I would recommend adding the second commit to the backports as well.

I took that commit as well, thank you.

--
Thanks,
Sasha