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Subject: Re: [PATCH] libsas: flush pending destruct work in
 sas_unregister_domain_devices()
To: Cong Wang <xiyou.wangcong@gmail.com>,
        John Garry <john.garry@huawei.com>
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CC: Johannes Thumshirn <jthumshirn@suse.de>,
        LKML <linux-kernel@vger.kernel.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Praveen Murali <pmurali@logicube.com>,
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        chenxiang <chenxiang66@hisilicon.com>
From: Jason Yan <yanaijie@huawei.com>
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Date: Fri, 8 Dec 2017 15:54:54 +0800
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On 2017/12/8 6:57, Cong Wang wrote:
> On Thu, Dec 7, 2017 at 5:37 AM, John Garry <john.garry@huawei.com> wrote:
>> On 28/11/2017 17:04, Cong Wang wrote:
>>>
>>> I don't understand, the only caller of sas_unregister_domain_devices()
>>> is sas_deform_port().
>>>
>>
>> And sas_deform_port() may be called from another worker on the same queue,
>> right? As in sas_phye_loss_of_signal()->sas_deform_port()
>
> Oh, good catch! I didn't notice this subtle call path.
>
> Do you have any better idea to fix this? We saw this on 4.9 too.
>

We have sent a patchset to fix this and to enhance libsas hotplug.
Please refer to https://lkml.org/lkml/2017/9/6/142

And I'm going to send a new version soon.

Jason

>>
>> The device destruct takes place in a separate worker from which
>> sas_deform_port() is called, but the same queue. So we have this queued
>> destruct happen after the port is fully deformed -> hence the WARN.
>>
>> I guess you only tested your patch on disks attached through an expander.
>
> I have very limited scsi hardware, so my testing is limited too.
>
> .
>