Revert "PCI: Avoid race while enabling upstream bridges"

This reverts commit 40f11adc7cd9281227f0a6a627d966dd0a5f0cd9.

Jens found that iwlwifi firmware loading failed on a Lenovo X1 Carbon,
gen4:

  iwlwifi 0000:04:00.0: Direct firmware load for iwlwifi-8000C-34.ucode failed with error -2
  iwlwifi 0000:04:00.0: Direct firmware load for iwlwifi-8000C-33.ucode failed with error -2
  iwlwifi 0000:04:00.0: Direct firmware load for iwlwifi-8000C-32.ucode failed with error -2
  iwlwifi 0000:04:00.0: loaded firmware version 31.532993.0 op_mode iwlmvm
  iwlwifi 0000:04:00.0: Detected Intel(R) Dual Band Wireless AC 8260, REV=0x208
  ...
  iwlwifi 0000:04:00.0: Failed to load firmware chunk!
  iwlwifi 0000:04:00.0: Could not load the [0] uCode section
  iwlwifi 0000:04:00.0: Failed to start INIT ucode: -110
  iwlwifi 0000:04:00.0: Failed to run INIT ucode: -110

He bisected it to 40f11adc7cd9 ("PCI: Avoid race while enabling upstream
bridges").  Revert that commit to fix the regression.

Link: http://lkml.kernel.org/r/4bcbcbc1-7c79-09f0-5071-bc2f53bf6574@kernel.dk
Fixes: 40f11adc7cd9 ("PCI: Avoid race while enabling upstream bridges")
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: Srinath Mannam <srinath.mannam@broadcom.com>
CC: Jens Axboe <axboe@kernel.dk>
CC: Luca Coelho <luca@coelho.fi>
CC: Johannes Berg <johannes@sipsolutions.net>
CC: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b0002daa50f3bb98dd0c0e40488e033f00a2ee0a..6078dfc11b112a88aec1c58eb911de9f996b6644 100644 (file)
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -52,7 +52,6 @@ static void pci_pme_list_scan(struct work_struct *work);
 static LIST_HEAD(pci_pme_list);
 static DEFINE_MUTEX(pci_pme_list_mutex);
 static DECLARE_DELAYED_WORK(pci_pme_work, pci_pme_list_scan);
-static DEFINE_MUTEX(pci_bridge_mutex);
 
 struct pci_pme_device {
        struct list_head list;
@@ -1351,16 +1350,10 @@ static void pci_enable_bridge(struct pci_dev *dev)
        if (bridge)
                pci_enable_bridge(bridge);
 
-       /*
-        * Hold pci_bridge_mutex to prevent a race when enabling two
-        * devices below the bridge simultaneously.  The race may cause a
-        * PCI_COMMAND_MEMORY update to be lost (see changelog).
-        */
-       mutex_lock(&pci_bridge_mutex);
        if (pci_is_enabled(dev)) {
                if (!dev->is_busmaster)
                        pci_set_master(dev);
-               goto end;
+               return;
        }
 
        retval = pci_enable_device(dev);
@@ -1368,8 +1361,6 @@ static void pci_enable_bridge(struct pci_dev *dev)
                dev_err(&dev->dev, "Error enabling bridge (%d), continuing\n",
                        retval);
        pci_set_master(dev);
-end:
-       mutex_unlock(&pci_bridge_mutex);
 }
 
 static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
@@ -1394,7 +1385,7 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
                return 0;               /* already enabled */
 
        bridge = pci_upstream_bridge(dev);
-       if (bridge && !pci_is_enabled(bridge))
+       if (bridge)
                pci_enable_bridge(bridge);
 
        /* only skip sriov related */