linux-kernel - Re: [RFC 0/3] acpipcihp: fix kernel crash on 2nd resume

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Date:   Tue, 25 Jul 2023 11:59:56 -0400
From:   Woody Suwalski <terraluna977@...il.com>
To:     Igor Mammedov <imammedo@...hat.com>
Cc:     linux-kernel@...r.kernel.org, bhelgaas@...gle.com,
        linux-pci@...r.kernel.org, mst@...hat.com,
        Woody Suwalski <terraluna977@...il.com>
Subject: Re: [RFC 0/3] acpipcihp: fix kernel crash on 2nd resume

Igor Mammedov wrote:
> On Tue, 25 Jul 2023 09:51:53 -0400
> Woody Suwalski <terraluna977@...il.com> wrote:
>
>> Igor Mammedov wrote:
>>> Changelog:
>>>     * split out debug patch into a separate one with extra printk added
>>>     * fixed inverte bus->self check (probably a reason why it didn't work before)
>>>
>>>
>>> 1/3 debug patch
>>> 2/3 offending patch
>>> 3/3 potential fix
>>>     
>>> I added more files to trace, add following to kernel CLI
>>>      dyndbg="file drivers/pci/access.c +p; file drivers/pci/hotplug/acpiphp_glue.c +p; file drivers/pci/bus.c +p; file drivers/pci/pci.c +p; file drivers/pci/setup-bus.c +p; file drivers/acpi/bus.c +p" ignore_loglevel
>>>
>>> should be applied on top of
>>>      e8afd0d9fccc PCI: pciehp: Cancel bringup sequence if card is not present
>>>
>>> apply a patch one by one and run testcase + capture dmesg after each patch
>>> one shpould endup with 3 dmesg to ananlyse
>>>    1st - old behaviour - no crash
>>>    2nd - crash
>>>    3rd - no crash hopefully
>>>
>>> Igor Mammedov (3):
>>>     acpiphp: extra debug hack
>>>     PCI: acpiphp: Reassign resources on bridge if necessary
>>>     acpipcihp: use __pci_bus_assign_resources() if bus doesn't have bridge
>>>
>>>    drivers/pci/hotplug/acpiphp_glue.c | 23 ++++++++++++++++++-----
>>>    1 file changed, 18 insertions(+), 5 deletions(-)
>>>   
>> Actually applying patch1 is already creating the crash (why???),
> probably it's due to an extra debug line, I've added.
> I dropped suspicions one, can you try again and see if it works.
>
>> hence I
>> have added also dmesg-6.5-0.txt which shows a working condition based on
>> git e8afd0d9fccc level (acpiphp_glue in kernel 6.4)
>>
>> Patch3 did not fix the issue, it seems that the culprit is somewhere
>> else triggered by  "benign" patch1 :-(
>>
>> Also note about the trigger description in patch3: the dmesg trace on
>> Inspiron laptop is collected after the first wake from suspend to ram.
>> The consecutive  attempt to sleep results in a frozen system.
> Thanks for clarification, I'll correct commit message once culprit
> is found.
>
Good news. After removing the botched debug statement which was masking 
the original issue, the testing went as you have predicted, and on patch 
3 system suspends to RAM OK.

Here are the requested 3 dmesg outputs, #2 is for the bad run.

I can retest with a final version of the patch once you have it ready...

Thanks, Woody


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