linux-kernel - Re: [PATCH v2 4/4] PCI: Check if the pci device get removed from pci tree already in remove

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Date:	Wed, 8 May 2013 15:32:31 -0700
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Gu Zheng <guz.fnst@...fujitsu.com>
Cc:	Yinghai Lu <yinghai@...nel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Taku Izumi <izumi.taku@...fujitsu.com>,
	tangchen <tangchen@...fujitsu.com>,
	Lin Feng <linfeng@...fujitsu.com>,
	Jiang Liu <jiang.liu@...wei.com>
Subject: Re: [PATCH v2 4/4] PCI: Check if the pci device get removed from pci
 tree already in remove_callback()

On Tue, Apr 30, 2013 at 4:31 AM, Gu Zheng <guz.fnst@...fujitsu.com> wrote:
> From a870da3615988f53a8949e5f8c907b079162067b Mon Sep 17 00:00:00 2001
> From: Gu Zheng <guz.fnst@...fujitsu.com>
> Date: Tue, 30 Apr 2013 18:45:12 +0800
> Subject: [PATCH v2 4/4] PCI: Check if the pci device get removed from pci tree already in remove_callback
> We found nested removing through:
>         echo -n 1 > /sys/bus/pci/devices/0000\:10\:00.0/remove ; echo -n 1 >
> /sys/bus/pci/devices/0000\:1a\:01.0/remove
>
> will cause kernel crash as bus get freed.
>
> [  418.946462] CPU 4
> [  418.968377] Pid: 512, comm: kworker/u:2 Tainted: G        W    3.8.0 #2
> FUJITSU-SV PRIMEQUEST 1800E/SB
> [  419.081763] RIP: 0010:[<ffffffff8137972e>]  [<ffffffff8137972e>]
> pci_bus_read_config_word+0x5e/0x90
> [  420.494137] Call Trace:
> [  420.523326]  [<ffffffff813851ef>] ? remove_callback+0x1f/0x40
> [  420.591984]  [<ffffffff8138044b>] pci_pme_active+0x4b/0x1c0
> [  420.658545]  [<ffffffff8137d8e7>] pci_stop_bus_device+0x57/0xb0
> [  420.729259]  [<ffffffff8137dab6>] pci_stop_and_remove_bus_device+0x16/0x30
> [  420.811392]  [<ffffffff813851fb>] remove_callback+0x2b/0x40
> [  420.877955]  [<ffffffff81257a56>] sysfs_schedule_callback_work+0x26/0x70
>
> https://bugzilla.kernel.org/show_bug.cgi?id=54411
>
> We have one patch that will let device hold bus ref to prevent it from
> being freed, but that will still generate warning.
>
> ------------[ cut here ]------------
> WARNING: at lib/list_debug.c:53 __list_del_entry+0x63/0xd0()
> Hardware name: PRIMEQUEST 1800E
> list_del corruption, ffff8807d1b6c000->next is LIST_POISON1 (dead000000100100)
> Call Trace:
>  [<ffffffff81056d4f>] warn_slowpath_common+0x7f/0xc0
>  [<ffffffff81056e46>] warn_slowpath_fmt+0x46/0x50
>  [<ffffffff81280b13>] __list_del_entry+0x63/0xd0
>  [<ffffffff81280b91>] list_del+0x11/0x40
>  [<ffffffff81298331>] pci_destroy_dev+0x31/0xc0
>  [<ffffffff812985bb>] pci_remove_bus_device+0x5b/0x70
>  [<ffffffff812985ee>] pci_stop_and_remove_bus_device+0x1e/0x30
>  [<ffffffff8129fc89>] remove_callback+0x29/0x40
>  [<ffffffff811f3b84>] sysfs_schedule_callback_work+0x24/0x70
>
> We can just check if the device get removed from pci tree
> already in the protection under pci_remove_rescan_mutex.
>
>
> Signed-off-by: Gu Zheng <guz.fnst@...fujitsu.com>
> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> ---
>  drivers/pci/pci-sysfs.c |   13 ++++++++++---
>  1 files changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index 5b4a9d9..18590c1 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -328,10 +328,17 @@ dev_rescan_store(struct device *dev, struct device_attribute *attr,
>
>  static void remove_callback(struct device *dev)
>  {
> -       struct pci_dev *pdev = to_pci_dev(dev);
> -
> +       struct pci_dev *pdev = to_pci_dev(dev), *tmp;
> +       bool found = false;
> +       struct pci_bus *bus = pdev->bus;
>         mutex_lock(&pci_remove_rescan_mutex);
> -       pci_stop_and_remove_bus_device(pdev);
> +       list_for_each_entry(tmp, &bus->devices, bus_list)
> +               if (tmp == pdev) {
> +                       found = true;
> +                       break;
> +               }
> +       if (found)
> +               pci_stop_and_remove_bus_device(pdev);

I assume this series won't be needed when we eventually get the
reference counting sorted out, because we shouldn't have to check
whether the device still exists.  Yinghai posted a
"fix_racing_removing_5.patch", which currently doesn't apply cleanly,
but I assume he'll refresh it after v3.10-rc1 is out.

Bjorn

>         mutex_unlock(&pci_remove_rescan_mutex);
>  }
>
> --
> 1.7.7
>
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