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From:   Dexuan-Linux Cui <dexuan.linux@gmail.com>
Date:   Tue, 12 Oct 2021 23:18:44 -0700
Message-ID: <CAA42JLZCE0CFUJHVZLT77YvPap49_cGiAMMt2E-B7X0tzST6jg@mail.gmail.com>
Subject: Re: PCI: Race condition in pci_create_sysfs_dev_files
To:     =?UTF-8?Q?Pali_Roh=C3=A1r?= <pali@kernel.org>
Cc:     Koen Vandeputte <koen.vandeputte@citymesh.com>,
        =?UTF-8?Q?Petr_=C5=A0tetiar?= <ynezz@true.cz>,
        Bjorn Helgaas <helgaas@kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>, linux-pci@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Gregory Clement <gregory.clement@bootlin.com>,
        Andrew Lunn <andrew@lunn.ch>,
        =?UTF-8?Q?Krzysztof_Wilczy=C5=84ski?= <kw@linux.com>,
        Yinghai Lu <yinghai@kernel.org>,
        Dexuan Cui <decui@microsoft.com>
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On Fri, Jun 25, 2021 at 4:55 AM Pali Roh=C3=A1r <pali@kernel.org> wrote:
>
> Hello!
>
> On Friday 25 June 2021 13:29:00 Koen Vandeputte wrote:
> > ...
> It is same race condition which I described in the first email of this
> email thread. I described exactly when it happens. I'm not able to
> trigger it with new kernels but as we know race conditions are hard to
> trigger...
>
> So result is that we know about it, just fix is not ready yet as it is
> not easy to fix it.
>
> Krzysztof has been working on fixing it, so maybe can provide an
> update...

I think we're seeing the same issue with a Linux VM on Hyper-V. Here
the kernel is https://git.launchpad.net/~canonical-kernel/ubuntu/+source/li=
nux-azure/+git/bionic/tree/?h=3DUbuntu-azure-5.4-5.4.0-1061.64_18.04.1

[    4.680707] hv_pci 47505500-0003-0000-3130-444531334632: PCI VMBus
probing: Using version 0x10002
[    4.730457] hv_pci 47505500-0003-0000-3130-444531334632: PCI host
bridge to bus 0003:00
[    4.735577] pci_bus 0003:00: root bus resource [mem
0x43000000-0x43ffffff window]
[    4.742189] pci_bus 0003:00: root bus resource [mem
0x1020000000-0x1031ffffff window]
[    4.747027] pci 0003:00:00.0: [10de:13f2] type 00 class 0x030000
[    4.770114] pci 0003:00:00.0: reg 0x10: [mem 0x43000000-0x43ffffff]
[    4.792153] pci 0003:00:00.0: reg 0x14: [mem
0x1020000000-0x102fffffff 64bit pref]
[    4.814022] pci 0003:00:00.0: reg 0x1c: [mem
0x1030000000-0x1031ffffff 64bit pref]
[    4.854830] pci 0003:00:00.0: Enabling HDA controller
[    4.869665] pci 0003:00:00.0: vgaarb: VGA device added:
decodes=3Dio+mem,owns=3Dmem,locks=3Dnone
[    4.879399] pci 0003:00:00.0: BAR 1: assigned [mem
0x1020000000-0x102fffffff 64bit pref]
[    4.903880] pci 0003:00:00.0: BAR 3: assigned [mem
0x1030000000-0x1031ffffff 64bit pref]
[    4.927977] pci 0003:00:00.0: BAR 0: assigned [mem 0x43000000-0x43ffffff=
]
[    4.938162] sysfs: cannot create duplicate filename
'/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A03:00/device:07/VMBUS:01/47505500-00=
03-0000-3130-444531334632/pci0003:00/0003:00:00.0/config'
[    4.951818] CPU: 0 PID: 135 Comm: kworker/0:2 Not tainted
5.4.0-1061-azure #64~18.04.1-Ubuntu
[    4.951820] Hardware name: Microsoft Corporation Virtual
Machine/Virtual Machine, BIOS 090007  06/02/2017
[    4.955812] Workqueue: hv_pri_chan vmbus_add_channel_work
[    4.955812] Call Trace:
[    4.955812]  dump_stack+0x57/0x6d
[    4.955812]  sysfs_warn_dup+0x5b/0x70
[    4.955812]  sysfs_add_file_mode_ns+0x158/0x180
[    4.955812]  sysfs_create_bin_file+0x64/0x90
[    4.955812]  pci_create_sysfs_dev_files+0x72/0x270
[    4.955812]  pci_bus_add_device+0x30/0x80
[    4.955812]  pci_bus_add_devices+0x31/0x70
[    4.955812]  hv_pci_probe+0x48c/0x650
[    4.955812]  vmbus_probe+0x3e/0x90
[    4.955812]  really_probe+0xf5/0x440
[    4.955812]  driver_probe_device+0x11b/0x130
[    4.955812]  __device_attach_driver+0x7b/0xe0
[    4.955812]  ? driver_allows_async_probing+0x60/0x60
[    4.955812]  bus_for_each_drv+0x6e/0xb0
[    4.955812]  __device_attach+0xe4/0x160
[    4.955812]  device_initial_probe+0x13/0x20
[    4.955812]  bus_probe_device+0x92/0xa0
[    4.955812]  device_add+0x402/0x690
[    4.955812]  device_register+0x1a/0x20
[    4.955812]  vmbus_device_register+0x5e/0xf0
[    4.955812]  vmbus_add_channel_work+0x2c4/0x640
[    4.955812]  process_one_work+0x209/0x400
[    4.955812]  worker_thread+0x34/0x400
[    4.955812]  kthread+0x121/0x140
[    4.955812]  ? process_one_work+0x400/0x400
[    4.955812]  ? kthread_park+0x90/0x90
[    4.955812]  ret_from_fork+0x35/0x40

Thanks,
Dexuan