PCI: sysfs: Ignore lockdep for remove attribute [Linux 4.9.187]

This Linux kernel change "PCI: sysfs: Ignore lockdep for remove attribute" is included in the Linux 4.9.187 release. This change is authored by Marek Vasut <marek.vasut+renesas [at] gmail.com> on Mon May 27 00:51:51 2019 +0200. The commit for this change in Linux stable tree is 2abc45e (patch) which is from upstream commit dc6b698. The same Linux upstream change may have been applied to various maintained Linux releases and you can find all Linux releases containing changes from upstream dc6b698.

PCI: sysfs: Ignore lockdep for remove attribute

[ Upstream commit dc6b698a86fe40a50525433eb8e92a267847f6f9 ]

With CONFIG_PROVE_LOCKING=y, using sysfs to remove a bridge with a device
below it causes a lockdep warning, e.g.,

  # echo 1 > /sys/class/pci_bus/0000:00/device/0000:00:00.0/remove
  ============================================
  WARNING: possible recursive locking detected
  ...
  pci_bus 0000:01: busn_res: [bus 01] is released

The remove recursively removes the subtree below the bridge.  Each call
uses a different lock so there's no deadlock, but the locks were all
created with the same lockdep key so the lockdep checker can't tell them
apart.

Mark the "remove" sysfs attribute with __ATTR_IGNORE_LOCKDEP() as it is
safe to ignore the lockdep check between different "remove" kernfs
instances.

There's discussion about a similar issue in USB at [1], which resulted in
356c05d58af0 ("sysfs: get rid of some lockdep false positives") and
e9b526fe7048 ("i2c: suppress lockdep warning on delete_device"), which do
basically the same thing for USB "remove" and i2c "delete_device" files.

[1] https://lore.kernel.org/r/[email protected]
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Marek Vasut <[email protected]>
[bhelgaas: trim commit log, details at above links]
Signed-off-by: Bjorn Helgaas <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Phil Edworthy <[email protected]>
Cc: Simon Horman <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Wolfram Sang <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>

There are 2 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/pci/pci-sysfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index e5d8e2e..7175401 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -371,7 +371,7 @@ static ssize_t remove_store(struct device *dev, struct device_attribute *attr,
        pci_stop_and_remove_bus_device_locked(to_pci_dev(dev));
    return count;
 }
-static struct device_attribute dev_remove_attr = __ATTR(remove,
+static struct device_attribute dev_remove_attr = __ATTR_IGNORE_LOCKDEP(remove,
                            (S_IWUSR|S_IWGRP),
                            NULL, remove_store);

Leave a Reply

Your email address will not be published. Required fields are marked *