Re: [PATCH v2 4/4] PCI: Check if the pci device get removed from pci tree already in remove_callback()

[Gu Zheng <guz.fnst@cn.fujitsu.com>]

On 05/09/2013 06:32 AM, Bjorn Helgaas wrote:

> On Tue, Apr 30, 2013 at 4:31 AM, Gu Zheng <guz.fnst@cn.fujitsu.com> wrote:
>> From a870da3615988f53a8949e5f8c907b079162067b Mon Sep 17 00:00:00 2001
>> From: Gu Zheng <guz.fnst@cn.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@cn.fujitsu.com>
>> Signed-off-by: Yinghai Lu <yinghai@kernel.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.  

Yes, your are right! Thanks for your correction.

>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.

OK, let's wait and see! :)

Best regards,
Gu

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