Re: [PATCH] libsas: flush pending destruct work in sas_unregister_domain_devices()

[Cong Wang]

On Tue, Nov 28, 2017 at 3:18 AM, John Garry <john.garry@xxxxxxxxxx> wrote:
> On 28/11/2017 08:20, Johannes Thumshirn wrote:
>>
>> On Mon, Nov 27, 2017 at 04:24:45PM -0800, Cong Wang wrote:
>>>
>>> We saw dozens of the following kernel waring:
>>>
>>>  WARNING: CPU: 0 PID: 705 at fs/sysfs/group.c:224
>>> sysfs_remove_group+0x54/0x88()
>>>  sysfs group ffffffff81ab7670 not found for kobject '6:0:3:0'
>>>  Modules linked in: cpufreq_ondemand x86_pkg_temp_thermal coretemp
>>> kvm_intel kvm microcode raid0 iTCO_wdt iTCO_vendor_support sb_edac edac_core
>>> lpc_ich mfd_core ioatdma i2c_i801 shpchp wmi hed acpi_cpufreq lp parport
>>> tcp_diag inet_diag ipmi_si ipmi_devintf ipmi_msghandler sch_fq_codel igb ptp
>>> pps_core i2c_algo_bit i2c_core crc32c_intel isci libsas scsi_transport_sas
>>> dca ipv6
>>>  CPU: 0 PID: 705 Comm: kworker/u240:0 Not tainted 4.1.35.el7.x86_64 #1
>>
>>
>> This should by now be fixed with commit fbce4d97fd43 ("scsi: fixup kernel
>> warning during rmmod()" which went into v4.14-rc6.
>>
>
> Is that the same issue? I think Cong Wang is just trying to deal with the
> longstanding libsas hotplug WARN.

Right, we saw it on both 4.1 and 3.14, clearly an old bug.


>
> We at Huawei are still working to fix it. Our patchset is under internal
> test at the moment.
>
> As for this patch:
>>  drivers/scsi/libsas/sas_discover.c | 7 ++++++-
>>  1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/scsi/libsas/sas_discover.c
>> b/drivers/scsi/libsas/sas_discover.c
>> index 60de66252fa2..27c11fc7aa2b 100644
>> --- a/drivers/scsi/libsas/sas_discover.c
>> +++ b/drivers/scsi/libsas/sas_discover.c
>> @@ -388,6 +388,11 @@ void sas_unregister_dev(struct asd_sas_port *port,
>> struct domain_device *dev)
>>       }
>>  }
>>
>> +static void sas_flush_work(struct asd_sas_port *port)
>> +{
>> +     scsi_flush_work(port->ha->core.shost);
>> +}
>> +
>>  void sas_unregister_domain_devices(struct asd_sas_port *port, int gone)
>>  {
>>       struct domain_device *dev, *n;
>> @@ -401,8 +406,8 @@ void sas_unregister_domain_devices(struct asd_sas_port
>> *port, int gone)
>>       list_for_each_entry_safe(dev, n, &port->disco_list, disco_list_node)
>>               sas_unregister_dev(port, dev);
>>
>> +     sas_flush_work(port);
>
> How can this work as sas_unregister_domain_devices() may be called from the
> same workqueue which you're trying to flush?


I don't understand, the only caller of sas_unregister_domain_devices()
is sas_deform_port().