From: Jiang Liu <liu...@gmail.com>

This patch uses PCI bus lock mechanism to avoid race conditions when doing
PCI device/host bridge hotplug by acpiphp driver.

Signed-off-by: Jiang Liu <liu...@gmail.com>
---
 drivers/pci/hotplug/acpiphp_glue.c |   13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/hotplug/acpiphp_glue.c 
b/drivers/pci/hotplug/acpiphp_glue.c
index 73af337..0ea7ab1 100644
--- a/drivers/pci/hotplug/acpiphp_glue.c
+++ b/drivers/pci/hotplug/acpiphp_glue.c
@@ -800,11 +800,14 @@ static int __ref enable_device(struct acpiphp_slot *slot)
        if (slot->flags & SLOT_ENABLED)
                goto err_exit;
 
+       if (pci_bus_lock_states(bus, PCI_BUS_STATE_WORKING) < 0)
+               return -EINVAL;
+
        num = pci_scan_slot(bus, PCI_DEVFN(slot->device, 0));
        if (num == 0) {
                /* Maybe only part of funcs are added. */
                dbg("No new device found\n");
-               goto err_exit;
+               goto out_unlock;
        }
 
        max = acpiphp_max_busnr(bus);
@@ -862,8 +865,10 @@ static int __ref enable_device(struct acpiphp_slot *slot)
                pci_dev_put(dev);
        }
 
+out_unlock:
+       pci_bus_unlock(bus);
 
- err_exit:
+err_exit:
        return retval;
 }
 
@@ -906,6 +911,9 @@ static int disable_device(struct acpiphp_slot *slot)
        struct pci_dev *pdev;
        struct pci_bus *bus = slot->bridge->pci_bus;
 
+       if (pci_bus_lock_states(bus, PCI_BUS_STATE_WORKING) < 0)
+               goto err_exit;
+
        /* The slot will be enabled when func 0 is added, so check
           func 0 before disable the slot. */
        pdev = pci_get_slot(bus, PCI_DEVFN(slot->device, 0));
@@ -943,6 +951,7 @@ static int disable_device(struct acpiphp_slot *slot)
        }
 
        slot->flags &= (~SLOT_ENABLED);
+       pci_bus_unlock(bus);
 
 err_exit:
        return 0;
-- 
1.7.9.5

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