Re: [PATCH v2 04/10] PCI: Destroy pci dev only once

[Bjorn Helgaas]

On Mon, Nov 25, 2013 at 6:28 PM, Yinghai Lu <yinghai@xxxxxxxxxx> wrote:
> Mutliple removing via /sys will call pci_destroy_dev two times.
>
> | When concurent removing pci devices which are in the same pci subtree
> | via sysfs, such as:
> | echo -n 1 > /sys/bus/pci/devices/0000\:10\:00.0/remove ; echo -n 1 >
> | /sys/bus/pci/devices/0000\:1a\:01.0/remove
> | (1a:01.0 device is downstream from the 10:00.0 bridge)
> |
> | the following warning will show:
> | [ 1799.280918] ------------[ cut here ]------------
> | [ 1799.336199] WARNING: CPU: 7 PID: 126 at lib/list_debug.c:53 __list_del_entry+0x63/0xd0()
> | [ 1799.433093] list_del corruption, ffff8807b4a7c000->next is LIST_POISON1 (dead000000100100)
> | [ 1800.276623] CPU: 7 PID: 126 Comm: kworker/u512:1 Tainted: G        W    3.12.0-rc5+ #196
> | [ 1800.508918] Workqueue: sysfsd sysfs_schedule_callback_work
> | [ 1800.574703]  0000000000000009 ffff8807adbadbd8 ffffffff8168b26c ffff8807c27d08a8
> | [ 1800.663860]  ffff8807adbadc28 ffff8807adbadc18 ffffffff810711dc ffff8807adbadc68
> | [ 1800.753130]  ffff8807b4a7c000 ffff8807b4a7c000 ffff8807ad089c00 0000000000000000
> | [ 1800.842282] Call Trace:
> | [ 1800.871651]  [<ffffffff8168b26c>] dump_stack+0x55/0x76
> | [ 1800.933301]  [<ffffffff810711dc>] warn_slowpath_common+0x8c/0xc0
> | [ 1801.005283]  [<ffffffff810712c6>] warn_slowpath_fmt+0x46/0x50
> | [ 1801.074081]  [<ffffffff8135a343>] __list_del_entry+0x63/0xd0
> | [ 1801.141839]  [<ffffffff8135a3c1>] list_del+0x11/0x40
> | [ 1801.201320]  [<ffffffff813734da>] pci_remove_bus_device+0x6a/0xe0
> | [ 1801.274279]  [<ffffffff8137356e>] pci_stop_and_remove_bus_device+0x1e/0x30
> | [ 1801.356606]  [<ffffffff8137b20b>] remove_callback+0x2b/0x40
> | [ 1801.423412]  [<ffffffff81251848>] sysfs_schedule_callback_work+0x18/0x60
> | [ 1801.503744]  [<ffffffff8108eab5>] process_one_work+0x1f5/0x540
> | [ 1801.573640]  [<ffffffff8108ea53>] ? process_one_work+0x193/0x540
> | [ 1801.645616]  [<ffffffff8108f2ac>] worker_thread+0x11c/0x370
> | [ 1801.712337]  [<ffffffff8108f190>] ? rescuer_thread+0x350/0x350
> | [ 1801.782178]  [<ffffffff8109731d>] kthread+0xed/0x100
> | [ 1801.841661]  [<ffffffff81097230>] ? kthread_create_on_node+0x160/0x160
> | [ 1801.919919]  [<ffffffff8169cc3c>] ret_from_fork+0x7c/0xb0
> | [ 1801.984608]  [<ffffffff81097230>] ? kthread_create_on_node+0x160/0x160
> | [ 1802.062825] ---[ end trace d77f2054de000fb7 ]---
> |
> | This issue is related to the bug 54411:
> | https://bugzilla.kernel.org/show_bug.cgi?id=54411
>
> Add is_removed to record if pci_destroy_dev is called already.
>
> During second calling, still have extra dev ref hold via
> device_schedule_call, so we are safe to check dev->is_removed.
>
> It fixs the problem In Gu's test.
>
> -v2: add partial changelog from Gu Zheng <guz.fnst@xxxxxxxxxxxxxx>
>      refresh after patch of moving device_del from Rafael.
>
> Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
> ---
>  drivers/pci/remove.c | 8 +++++---
>  include/linux/pci.h  | 1 +
>  2 files changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
> index f452148..b090cec 100644
> --- a/drivers/pci/remove.c
> +++ b/drivers/pci/remove.c
> @@ -20,9 +20,11 @@ static void pci_stop_dev(struct pci_dev *dev)
>
>  static void pci_destroy_dev(struct pci_dev *dev)
>  {
> -       device_del(&dev->dev);
> -
> -       put_device(&dev->dev);
> +       if (!dev->is_removed) {
> +               device_del(&dev->dev);
> +               dev->is_removed = 1;

As Rafael pointed out, this looks like a race.  What prevents two
concurrent calls to pci_destroy_dev() from seeing "dev->is_removed ==
0" and both calling device_del() on the same device?

> +               put_device(&dev->dev);
> +       }
>  }
>
>  void pci_remove_bus(struct pci_bus *bus)
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 1084a15..ccb316d 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -321,6 +321,7 @@ struct pci_dev {
>         unsigned int    multifunction:1;/* Part of multi-function device */
>         /* keep track of device state */
>         unsigned int    is_added:1;
> +       unsigned int    is_removed:1;   /* pci_destroy_dev is called */
>         unsigned int    is_busmaster:1; /* device is busmaster */
>         unsigned int    no_msi:1;       /* device may not use msi */
>         unsigned int    block_cfg_access:1;     /* config space access is blocked */
> --
> 1.8.1.4
>
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