The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From aeae4f3e5c38d47bdaef50446dc0ec857307df68 Mon Sep 17 00:00:00 2001

From: Lukas Wunner lukas@wunner.de Date: Tue, 4 Sep 2018 12:34:18 -0500 Subject: [PATCH] PCI/ASPM: Fix link_state teardown on device removal

Upon removal of the last device on a bus, the link_state of the bridge leading to that bus is sought to be torn down by having pci_stop_dev() call pcie_aspm_exit_link_state().

When ASPM was originally introduced by commit 7d715a6c1ae5 ("PCI: add PCI Express ASPM support"), it determined whether the device being removed is the last one by calling list_empty() on the bridge's subordinate devices list. That didn't work because the device is only removed from the list slightly later in pci_destroy_dev().

Commit 3419c75e15f8 ("PCI: properly clean up ASPM link state on device remove") attempted to fix it by calling list_is_last(), but that's not correct either because it checks whether the device is at the *end* of the list, not whether it's the last one *left* in the list. If the user removes the device which happens to be at the end of the list via sysfs but other devices are preceding the device in the list, the link_state is torn down prematurely.

The real fix is to move the invocation of pcie_aspm_exit_link_state() to pci_destroy_dev() and reinstate the call to list_empty(). Remove a duplicate check for dev->bus->self because pcie_aspm_exit_link_state() already contains an identical check.

Fixes: 7d715a6c1ae5 ("PCI: add PCI Express ASPM support") Signed-off-by: Lukas Wunner lukas@wunner.de Signed-off-by: Bjorn Helgaas bhelgaas@google.com Cc: Shaohua Li shaohua.li@intel.com Cc: stable@vger.kernel.org # v2.6.26

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c index 5326916715d2..f78860ce884b 100644 --- a/drivers/pci/pcie/aspm.c +++ b/drivers/pci/pcie/aspm.c @@ -991,7 +991,7 @@ void pcie_aspm_exit_link_state(struct pci_dev *pdev) * All PCIe functions are in one slot, remove one function will remove * the whole slot, so just wait until we are the last function left. */ - if (!list_is_last(&pdev->bus_list, &parent->subordinate->devices)) + if (!list_empty(&parent->subordinate->devices)) goto out;

link = parent->link_state; diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c index 461e7fd2756f..e9c6b120cf45 100644 --- a/drivers/pci/remove.c +++ b/drivers/pci/remove.c @@ -25,9 +25,6 @@ static void pci_stop_dev(struct pci_dev *dev)

pci_dev_assign_added(dev, false); } - - if (dev->bus->self) - pcie_aspm_exit_link_state(dev); }

static void pci_destroy_dev(struct pci_dev *dev) @@ -41,6 +38,7 @@ static void pci_destroy_dev(struct pci_dev *dev) list_del(&dev->bus_list); up_write(&pci_bus_sem);

+ pcie_aspm_exit_link_state(dev); pci_bridge_d3_update(dev); pci_free_resources(dev); put_device(&dev->dev);