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Date:   Mon, 17 Feb 2020 10:31:56 +0100
From:   Niklas Schnelle <>
To:     Sasha Levin <>
        Peter Oberparleiter <>,
        Vasily Gorbik <>,
Subject: Re: [PATCH AUTOSEL 5.5 094/542] s390/pci: Fix possible deadlock in

On Fri, Feb 14, 2020 at 10:41:26AM -0500, Sasha Levin wrote:
> From: Niklas Schnelle <>
> [ 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:

("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.

Niklas Schnelle
Niklas Schnelle
Linux on Z Development

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