[PATCH 2/2] PCIe hotplug interrupt and AER pci_slot_mutex deadlock

[Ian May <ian.may@canonical.com>]

In the AER recovery code path, pci_bus_error_reset acquires the pci_slot_mutex,
unlock and relock in call to pci_slot_reset around controller reset to lock in
same order as the hotplug code path.

        Hotplug                                AER
----------------------------       ---------------------------
down_read(&ctrl->reset_lock)	   mutex_lock(&pci_slot_mutex)
mutex_lock(&pci_slot_mutex)	   down_write(&ctrl->reset_lock)

Signed-off-by: Ian May <ian.may@canonical.com>
---
 drivers/pci/pci.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index e32c5a1a706e..4eeca8b18664 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5229,6 +5229,7 @@ static int pci_slot_reset(struct pci_slot *slot, int probe)
 
 	if (!probe)
 	{
+		mutex_unlock(&pci_slot_mutex);
 		slot->hotplug->ops->reset_lock(slot->hotplug);
 		pci_slot_lock(slot);
 	}
@@ -5241,6 +5242,7 @@ static int pci_slot_reset(struct pci_slot *slot, int probe)
 	{
 		pci_slot_unlock(slot);
 		slot->hotplug->ops->reset_unlock(slot->hotplug);
+		mutex_lock(&pci_slot_mutex);
 	}
 
 	return rc;
-- 
2.25.1