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

From: Sasha Levin
Date: Thu Feb 20 2020 - 11:11:43 EST

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


attribute vs powering it off via


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:

("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.