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    SubjectRe: [PATCH AUTOSEL 5.5 094/542] s390/pci: Fix possible deadlock in recover_store()
    On Fri, Feb 14, 2020 at 10:41:26AM -0500, Sasha Levin wrote:
    > From: Niklas Schnelle <schnelle@linux.ibm.com>
    >
    > [ 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.

    Thanks,
    Niklas Schnelle
    --
    Niklas Schnelle
    Linux on Z Development

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