linux-kernel - Re: [PATCH 1/2] PCI: ASPM exit link state code could skip devices

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Message-ID: <CAErSpo7OYFF7YGDneoTvVjhxMq1q92UewddseLrx_w7VJ+JOBA@mail.gmail.com>
Date:	Fri, 1 Feb 2013 15:31:41 -0700
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Joe Lawrence <Joe.Lawrence@...atus.com>
Cc:	Myron Stowe <mstowe@...hat.com>, linux-pci@...r.kernel.org,
	Matthew Garrett <mjg59@...f.ucam.org>,
	David Bulkow <david.bulkow@...atus.com>, shli@...nel.org,
	shli@...ionio.com, kaneshige.kenji@...fujitsu.com,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] PCI: ASPM exit link state code could skip devices

On Fri, Feb 1, 2013 at 12:55 PM, Joe Lawrence <Joe.Lawrence@...atus.com> wrote:
> On Thu, 31 Jan 2013, Myron Stowe wrote:

>> PCI: ASPM exit link state code is skipping devices
>>
>> From: Myron Stowe <myron.stowe@...hat.com>
>>
>> On PCI bus hotplug removal, 'pcie_aspm_exit_link_state' can potentially
>> skip parent devices that have link_state allocated.  Instead of exiting
>> early if a given device in not PCIe, check whether or not the device's
>> parent has link_state allocated.  This enables 'pcie_aspm_exit_link_state'
>> to properly clean up parent link_state when the last function in a slot
>> might not be PCIe.
>>
>> Reported-by: Joe Lawrence <joe.lawrence@...atus.com>
>> Signed-off-by: Myron Stowe <myron.stowe@...hat.com>
>> ---
>>
>>  drivers/pci/pcie/aspm.c |    5 +----
>>  1 files changed, 1 insertions(+), 4 deletions(-)
>>
>>
>> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
>> index 8474b6a..aa52727 100644
>> --- a/drivers/pci/pcie/aspm.c
>> +++ b/drivers/pci/pcie/aspm.c
>> @@ -634,10 +634,7 @@ void pcie_aspm_exit_link_state(struct pci_dev *pdev)
>>       struct pci_dev *parent = pdev->bus->self;
>>       struct pcie_link_state *link, *root, *parent_link;
>>
>> -     if (!pci_is_pcie(pdev) || !parent || !parent->link_state)
>> -             return;
>> -     if ((pci_pcie_type(parent) != PCI_EXP_TYPE_ROOT_PORT) &&
>> -         (pci_pcie_type(parent) != PCI_EXP_TYPE_DOWNSTREAM))
>> +     if (!parent || !parent->link_state)
>>               return;
>>
>>       down_read(&pci_bus_sem);
>>
>>
>>
>
> Hi Myron,
>
> The patch tests eliminates the reported crash when hotplugging our
> problem PCI bus.
>
> The additional checks removed from pcie_aspm_exit_link_state (ie, the
> simplification) do appear to be unnecessary as pcie_aspm_init_link_state
> is already preventing such devices from allocating link state.

I added a Tested-by for you, Joe, and applied this to my pci/joe-aspm
branch for v3.9.  Thanks!
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