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

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-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>
> ---
> 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 */
>
>

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