powerpc/eeh: Fix deadlock when PE frozen state can't be cleared

In eeh_reset_device(), we take the pci_rescan_remove_lock immediately after
after we call eeh_reset_pe() to reset the PCI controller. We then call
eeh_clear_pe_frozen_state(), which can return an error. In this case, we
bail out of eeh_reset_device() without calling pci_unlock_rescan_remove().

Add a call to pci_unlock_rescan_remove() in the eeh_clear_pe_frozen_state()
error path so that we don't cause a deadlock later on.

Reported-by: Pradipta Ghosh <pradghos@in.ibm.com>
Fixes: 78954700631f ("powerpc/eeh: Avoid I/O access during PE reset")
Cc: stable@vger.kernel.org # v3.16+
Signed-off-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Acked-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 3 insertions, 1 deletions

diff --git a/arch/powerpc/kernel/eeh_driver.c b/arch/powerpc/kernel/eeh_driver.c
index a62be72da274..5c31369435f2 100644
--- a/arch/powerpc/kernel/eeh_driver.c
+++ b/arch/powerpc/kernel/eeh_driver.c
@@ -671,8 +671,10 @@ static int eeh_reset_device(struct eeh_pe *pe, struct pci_bus *bus,
 
         /* Clear frozen state */
         rc = eeh_clear_pe_frozen_state(pe, false);
-        if (rc)
+        if (rc) {
+                pci_unlock_rescan_remove();
                 return rc;
+        }
 
         /* Give the system 5 seconds to finish running the user-space
          * hotplug shutdown scripts, e.g. ifdown for ethernet.  Yes,