Re: [PATCH] pci: fix invalid list entry warning for double pci deviceremoving via sysfs

[Gu Zheng]

Hi Bjorn,
Thanks for your comments.:)
Please refer to inline.

Best regards,
Gu

On 10/31/2013 01:08 AM, Bjorn Helgaas wrote:

> On Wed, Oct 30, 2013 at 06:14:20PM +0800, Gu Zheng wrote:
>> 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)
>> [ 1799.532110] Modules linked in: nf_conntrack_netbios_ns nf_conntrack_broadcast ipt_MASQUERADE ip6table_mangle ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 iptable_nat nf_nat_ipv4 nf_nat iptable_mangle ipt_REJECT nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter ip_tables sg dm_mirror dm_region_hash dm_log dm_mod vfat fat e1000e igb iTCO_wdt iTCO_vendor_support ioatdma ptp i7core_edac ipmi_si edac_core lpc_ich pps_core i2c_i801 pcspkr mfd_core dca ipmi_msghandler acpi_cpufreq xfs libcrc32c sd_mod crc_t10dif crct10dif_common i2c_algo_bit drm_kms_helper ttm drm mptsas scsi_transport_sas mptscsih i2c_core megaraid_sas mptbase
>> [ 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
>>
>> Since we added the pci_bus reference management, the bug becomes a
>> invalid list entry warning as descripted above. Beacuse it still
>> trys to delete an deleted pci device from device list.
>>
>> So here we make stop device actually detach driver only, and remove
>> device will do device_del instead, and move bus_list change and pci device
>> resource free into pci_release_dev, so that it'll consistent with
>> bus reference managment, and the device only can be deleted from device
>> list in pci_release_dev just for one time.
> 
> You have a good argument for moving the &dev->bus_list maintenance from
> pci_destroy_dev() to pci_release_dev(), because I think we can call
> pci_destroy_dev() twice for the same device, and we don't want to do the
> list_del() twice.
> 
> I suspect we want to move other stuff, too, but you haven't explained
> why we need the device_del(), device_release_driver(), and
> pci_free_resources() changes.  Possibly similar arguments apply.  I'd
> rather see separate patches to move these pieces so we can think about
> them individually.

Sorry for missing explanation.
The reason of moving pci_free_resources() into pci_release_dev is that the original
place(pci_destory_dev()) is too early as there may be still others holding reference
as the case mentioned above.
Changing device_del() and device_release_driver() in order to make pci_stop_dev
just do one thing--release driver, but it seems this change is nonsense.:(

> 
>> Besides, it also makes hostbridge to use device_unregister to be pair
>> with device_register before.
> 
> Please split the host bridge changes into a separate patch.  One logical
> change, one patch.  If they *can* be split up, please split them up.

Agree all. Thanks for your suggestion, got it.

> 
>> This patch is based on Yinghai's privious similar patch:
>> http://lkml.org/lkml/2013/5/13/658
> 
> There are seven patches in that series.  I don't know which one you're
> referring to.

[2/7]~[4/7]

> 
> Please run a spell checker on your changelog.  There are many spelling
> errors.

Got it, Thanks very much.

> 
>> Signed-off-by: Gu Zheng <guz.fnst@xxxxxxxxxxxxxx>
>> ---
>>  drivers/pci/probe.c  | 23 +++++++++++++++++++++--
>>  drivers/pci/remove.c | 32 ++++++++------------------------
>>  2 files changed, 29 insertions(+), 26 deletions(-)
>>
>> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
>> index 7ef0f86..c639f44 100644
>> --- a/drivers/pci/probe.c
>> +++ b/drivers/pci/probe.c
>> @@ -1156,6 +1156,21 @@ static void pci_release_capabilities(struct pci_dev *dev)
>>  	pci_free_cap_save_buffers(dev);
>>  }
>>  
>> +static void pci_free_resources(struct pci_dev *dev)
>> +{
>> +	int i;
>> +
>> +	msi_remove_pci_irq_vectors(dev);
>> +
>> +	pci_cleanup_rom(dev);
>> +	for (i = 0; i < PCI_NUM_RESOURCES; i++) {
>> +		struct resource *res = dev->resource + i;
>> +
>> +		if (res->parent)
>> +			release_resource(res);
>> +	}
>> +}
>> +
>>  /**
>>   * pci_release_dev - free a pci device structure when all users of it are finished.
>>   * @dev: device that's been disconnected
>> @@ -1165,9 +1180,13 @@ static void pci_release_capabilities(struct pci_dev *dev)
>>   */
>>  static void pci_release_dev(struct device *dev)
>>  {
>> -	struct pci_dev *pci_dev;
>> +	struct pci_dev *pci_dev = to_pci_dev(dev);
>> +
>> +	down_write(&pci_bus_sem);
>> +	list_del(&pci_dev->bus_list);
>> +	up_write(&pci_bus_sem);
>> +	pci_free_resources(pci_dev);
>>  
>> -	pci_dev = to_pci_dev(dev);
>>  	pci_release_capabilities(pci_dev);
>>  	pci_release_of_node(pci_dev);
>>  	pcibios_release_device(pci_dev);
>> diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
>> index 8fc54b7..5659283 100644
>> --- a/drivers/pci/remove.c
>> +++ b/drivers/pci/remove.c
>> @@ -3,20 +3,6 @@
>>  #include <linux/pci-aspm.h>
>>  #include "pci.h"
>>  
>> -static void pci_free_resources(struct pci_dev *dev)
>> -{
>> -	int i;
>> -
>> - 	msi_remove_pci_irq_vectors(dev);
>> -
>> -	pci_cleanup_rom(dev);
>> -	for (i = 0; i < PCI_NUM_RESOURCES; i++) {
>> -		struct resource *res = dev->resource + i;
>> -		if (res->parent)
>> -			release_resource(res);
>> -	}
>> -}
>> -
>>  static void pci_stop_dev(struct pci_dev *dev)
>>  {
>>  	pci_pme_active(dev, false);
>> @@ -24,8 +10,7 @@ static void pci_stop_dev(struct pci_dev *dev)
>>  	if (dev->is_added) {
>>  		pci_proc_detach_device(dev);
>>  		pci_remove_sysfs_dev_files(dev);
>> -		device_del(&dev->dev);
>> -		dev->is_added = 0;
>> +		device_release_driver(&dev->dev);
>>  	}
>>  
>>  	if (dev->bus->self)
>> @@ -34,12 +19,11 @@ static void pci_stop_dev(struct pci_dev *dev)
>>  
>>  static void pci_destroy_dev(struct pci_dev *dev)
>>  {
>> -	down_write(&pci_bus_sem);
>> -	list_del(&dev->bus_list);
>> -	up_write(&pci_bus_sem);
>> -
>> -	pci_free_resources(dev);
>> -	put_device(&dev->dev);
>> +	if (dev->is_added) {
>> +		device_del(&dev->dev);
>> +		put_device(&dev->dev);
>> +		dev->is_added = 0;
> 
> This is wrong.  You can't reference dev->is_added after put_device()
> because you have to assume you are holding the only reference, and the
> pci_dev may be deallocated before put_device() returns.

Yes, you're right, it's a low mistake here, dev may be invalid after calling
put_device().

> 
>> +	}
>>  }
>>  
>>  void pci_remove_bus(struct pci_bus *bus)
>> @@ -126,7 +110,7 @@ void pci_stop_root_bus(struct pci_bus *bus)
>>  		pci_stop_bus_device(child);
>>  
>>  	/* stop the host bridge */
>> -	device_del(&host_bridge->dev);
>> +	device_release_driver(&host_bridge->dev);
>>  }
>>  
>>  void pci_remove_root_bus(struct pci_bus *bus)
>> @@ -145,5 +129,5 @@ void pci_remove_root_bus(struct pci_bus *bus)
>>  	host_bridge->bus = NULL;
>>  
>>  	/* remove the host bridge */
>> -	put_device(&host_bridge->dev);
>> +	device_unregister(&host_bridge->dev);
>>  }
>> -- 
>> 1.8.1
>>
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