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SubjectRe: [PATCH v11 1/8] PCI/ERR: Update error status after reset_link()
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Hi Bjorn,

Thanks for the comments.

On 1/3/20 6:54 PM, Bjorn Helgaas wrote:
> On Fri, Jan 03, 2020 at 05:03:03PM -0800, Kuppuswamy Sathyanarayanan wrote:
>> On 1/3/20 4:34 PM, Bjorn Helgaas wrote:
>>> On Thu, Dec 26, 2019 at 04:39:07PM -0800, sathyanarayanan.kuppuswamy@linux.intel.com wrote:
>>>> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
>>>>
>>>> Commit bdb5ac85777d ("PCI/ERR: Handle fatal error recovery") uses
>>>> reset_link() to recover from fatal errors. But, if the reset is
>>>> successful there is no need to continue the rest of the error recovery
>>>> checks. Also, during fatal error recovery, if the initial value of error
>>>> status is PCI_ERS_RESULT_DISCONNECT or PCI_ERS_RESULT_NO_AER_DRIVER then
>>>> even after successful recovery (using reset_link()) pcie_do_recovery()
>>>> will report the recovery result as failure. So update the status of
>>>> error after reset_link().
>>> I like the part about updating "status" with the result of
>>> reset_link(), and I split that into its own patch because it
>>> seems like a fix that *can* be separated.
>>>
>>> But I'm not convinced that we should skip the ->slot_reset()
>>> callbacks if the reset_link() was successful.
>> If reset_link() call is successful then the result value will be
>> "PCI_ERS_RESULT_RECOVERED". So even if you proceed with
>> rest of the code, slot_reset() will never get called right ?
> The current code:
>
> if (state == pci_channel_io_frozen &&
> reset_link(dev, service) != PCI_ERS_RESULT_RECOVERED)
> goto failed;
> ...
> if (status == PCI_ERS_RESULT_NEED_RESET) {
> status = PCI_ERS_RESULT_RECOVERED;
> pci_walk_bus(bus, report_slot_reset, &status);
>
> doesn't save the result of reset_link(), so if status was
> PCI_ERS_RESULT_NEED_RESET and the reset succeeds, we will call
> ->slot_reset().
>
> After your patch, if "state == pci_channel_io_frozen", we *never* call
> ->slot_reset().
>
> Do you think that matches pci-error-recovery.rst? It doesn't seem
> like it to me, but perhaps I haven't read it closely enough.
Documentation does not have clear details on what to do with return
value of reset_link() ( step 3). But IMO, if step 3 recovers the device and
returns PCI_ERS_RESULT_RECOVERED then there is no need to proceed
to slot reset (step 4). May be we should update the Documentation ?

Keith,
You have any comments ?
>
>>> According to
>>> Documentation/PCI/pci-error-recovery.rst, we should call
>>> ->slot_reset() after completion of the reset.
>>>
>>> For example, rsxx_err_handler implements ->slot_reset(), but
>>> not ->resume(). If we reset the device, we'll claim success and
>>> return, but we won't call rsxx_slot_reset(), which does a bunch
>>> of important-looking recovery stuff.
>>>
>>> If pci-error-recovery.rst is wrong, we should fix that (after
>>> auditing all the drivers to make sure they match).
>>>
>>>> Fixes: bdb5ac85777d ("PCI/ERR: Handle fatal error recovery")
>>>> Cc: Ashok Raj <ashok.raj@intel.com>
>>>> Cc: Keith Busch <keith.busch@intel.com>
>>>> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
>>>> Acked-by: Keith Busch <keith.busch@intel.com>
>>>> ---
>>>> drivers/pci/pcie/err.c | 10 +++++++---
>>>> 1 file changed, 7 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
>>>> index b0e6048a9208..53cd9200ec2c 100644
>>>> --- a/drivers/pci/pcie/err.c
>>>> +++ b/drivers/pci/pcie/err.c
>>>> @@ -204,9 +204,12 @@ void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
>>>> else
>>>> pci_walk_bus(bus, report_normal_detected, &status);
>>>> - if (state == pci_channel_io_frozen &&
>>>> - reset_link(dev, service) != PCI_ERS_RESULT_RECOVERED)
>>>> - goto failed;
>>>> + if (state == pci_channel_io_frozen) {
>>>> + status = reset_link(dev, service);
>>>> + if (status != PCI_ERS_RESULT_RECOVERED)
>>>> + goto failed;
>>>> + goto done;
>>>> + }
>>>> if (status == PCI_ERS_RESULT_CAN_RECOVER) {
>>>> status = PCI_ERS_RESULT_RECOVERED;
>>>> @@ -228,6 +231,7 @@ void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
>>>> if (status != PCI_ERS_RESULT_RECOVERED)
>>>> goto failed;
>>>> +done:
>>>> pci_dbg(dev, "broadcast resume message\n");
>>>> pci_walk_bus(bus, report_resume, &status);
>>>> --
>>>> 2.21.0
>>>>
>> --
>> Sathyanarayanan Kuppuswamy
>> Linux kernel developer
>>
--
Sathyanarayanan Kuppuswamy
Linux kernel developer

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