[PATCH] Revert "PCI: Avoid race while enabling upstream bridges"

2017-09-15 Thread Bjorn Helgaas 
This reverts commit 40f11adc7cd9281227f0a6a627d966dd0a5f0cd9.

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

  iwlwifi :04:00.0: Direct firmware load for iwlwifi-8000C-34.ucode failed 
with error -2
  iwlwifi :04:00.0: Direct firmware load for iwlwifi-8000C-33.ucode failed 
with error -2
  iwlwifi :04:00.0: Direct firmware load for iwlwifi-8000C-32.ucode failed 
with error -2
  iwlwifi :04:00.0: loaded firmware version 31.532993.0 op_mode iwlmvm
  iwlwifi :04:00.0: Detected Intel(R) Dual Band Wireless AC 8260, REV=0x208
  ...
  iwlwifi :04:00.0: Failed to load firmware chunk!
  iwlwifi :04:00.0: Could not load the [0] uCode section
  iwlwifi :04:00.0: Failed to start INIT ucode: -110
  iwlwifi :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-bc2f53bf6...@kernel.dk
Fixes: 40f11adc7cd9 ("PCI: Avoid race while enabling upstream bridges")
Signed-off-by: Bjorn Helgaas 
CC: Srinath Mannam 
CC: Jens Axboe 
CC: Luca Coelho 
CC: Johannes Berg 
CC: Emmanuel Grumbach 
---
 drivers/pci/pci.c |   13 ++---
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b0002daa50f3..6078dfc11b11 100644
--- 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 */

Re: [PATCH] Revert "PCI: Avoid race while enabling upstream bridges"

2017-09-15 Thread Konstantin Khlebnikov 

On 15.09.2017 10:23, Bjorn Helgaas wrote:

This reverts commit 40f11adc7cd9281227f0a6a627d966dd0a5f0cd9.

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

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


I've found this too. Bug in fast-path: reverting last hunk is enough
http://lkml.kernel.org/r/150547971091.977464.16294045866179907260.stgit@buzz



Link: http://lkml.kernel.org/r/4bcbcbc1-7c79-09f0-5071-bc2f53bf6...@kernel.dk
Fixes: 40f11adc7cd9 ("PCI: Avoid race while enabling upstream bridges")
Signed-off-by: Bjorn Helgaas 
CC: Srinath Mannam 
CC: Jens Axboe 
CC: Luca Coelho 
CC: Johannes Berg 
CC: Emmanuel Grumbach 
---
  drivers/pci/pci.c |   13 ++---
  1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b0002daa50f3..6078dfc11b11 100644
--- 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 */