linux-kernel - Re: PCI: Race condition in pci_create_sysfs_dev

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Date:   Wed, 6 Apr 2022 16:08:29 +0200
From:   Koen Vandeputte <koen.vandeputte@...ymesh.com>
To:     Krzysztof Hałasa <khalasa@...p.pl>,
        Bjorn Helgaas <helgaas@...nel.org>
Cc:     Pali Rohár <pali@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Andrew Lunn <andrew@...n.ch>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Dexuan Cui <dexuan.linux@...il.com>,
        Petr Štetiar <ynezz@...e.cz>,
        Piotr Dymacz <pepe2k@...il.com>
Subject: Re: PCI: Race condition in pci_create_sysfs_dev_files (can't boot)


On 01.04.22 15:50, Koen Vandeputte wrote:
>
> On 15.02.22 07:35, Krzysztof Hałasa wrote:
>> Hi Bjorn,
>>
>> Bjorn Helgaas <helgaas@...nel.org> writes:
>>
>>> Koen collected some interesting logs at
>>> https://lore.kernel.org/all/cd4812f0-1de3-0582-936c-ba30906595af@citymesh.com/ 
>>>
>>> They're from v5.10, which was before all of Krzysztof W's nice work
>>> converting to static attributes, but Koen's log shows the error
>>> happening in the pci_sysfs_init() initcall, which is *after*
>>> imx6_pcie_probe():
>>>
>>>    imx6_pcie_probe                # probably device initcall (level 6)
>>>      ...
>>>        pci_create_sysfs_dev_files
>>>
>>>    pci_sysfs_init                 # late initcall (level 7)
>>>      pci_create_sysfs_dev_files
>>>        "sysfs: cannot create duplicate filename"
>> Well, imx6_pcie_probe() is called indirectly by
>> platform_driver_register(). I guess it doesn't know about the initcall
>> ordering, after it's registered.
>>
>> It looks like the problem is the imx6_pcie_probe() (via
>> dw_pcie_host_init() -> pci_host_probe()) is interfering with
>> pci_sysfs_init(). This may eventually cause some invalid memory access
>> as well.
>>
>> BTW I thought for a moment that maybe 5.14 is free from this. I was
>> wrong. The problem doesn't manifest itself on my custom i.MX6 device
>> (using Tinyrex CPU module from Voipac/Fedevel, perhaps because I don't
>> use any PCI devices there). It does on Ventana SBC from Gateworks,
>> though. BTW the above (and below) is v5.16.
>>
>> It goes like this:
>> [0.096212] do_initcall_level: 6
>> [0.105625] imx6_pcie_init
>> [0.106106] imx6_pcie_probe <<<<<<<<<<<<<<<<<<<<<
>> [0.106412] imx6q-pcie 1ffc000.pcie: host bridge /soc/pcie@...c000 
>> ranges:
>>
>> [0.322613] imx6q-pcie 1ffc000.pcie: Link up
>> [0.322776] imx6q-pcie 1ffc000.pcie: PCI host bridge to bus 0000:00
>> [0.322790] pci_bus 0000:00: root bus resource [bus 00-ff]
>>
>> [0.405251] do_initcall_level: 6 ENDs but imx6_pcie_probe() still active
>> [0.405262] do_initcall_level: 7
>>
>> [0.410393] pci_sysfs_init <<<<<<<<<<<<<<<<<<<<<
>> [0.410423] pci 0000:00:00.0: pci_create_sysfs_dev_files
>>
>> [0.410532] [<8068091c>] (pci_create_sysfs_dev_files)
>> [0.410551] [<80918710>] (pci_sysfs_init)
>> [0.410568] [<8010166c>] (do_one_initcall)
>>
>> [0.410717] pci_sysfs_init END <<<<<<<<<<<<<<<<<<<<<
>>
>> [0.533843] [<803f1c74>] (pci_bus_add_devices)
>> [0.533862] [<803f574c>] (pci_host_probe)
>> [0.533879] [<80414310>] (dw_pcie_host_init)
>> [0.533895] [<80681ac8>] (imx6_pcie_probe)
>> [0.533915] [<8045e9e4>] (platform_probe)
>> (Repeats multiple times, I guess for each PCI device)
>>
>> [0.543893] imx6_pcie_probe END <<<<<<<<<<<<<<<<<<<<<
>>
>> [0.692244] do_initcall_level: 7 END
>
>
> Hi all,
>
> Any update on this topic?
> I just tested kernel 5.15 on imx6 (gateworks Ventana 5200) and as soon 
> as I connect a pcie device on one of the ports,
>
> following happens:
>
> https://pastebin.com/raw/mgfSvTRB
>
> Any idea if this is related?
>
>
> Thanks,
>
> Koen
>
Hi all,

I tested a bit more today and simply let the board reboot all day long.
After roughly 20 reboots, it suddenly booted once stable without any 
errors/warnings.

Looks like a race condition ..

Any idea?

Thanks,

Koen