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Date:   Fri, 8 Dec 2017 15:54:54 +0800
From:   Jason Yan <yanaijie@...wei.com>
To:     Cong Wang <xiyou.wangcong@...il.com>,
        John Garry <john.garry@...wei.com>
CC:     Johannes Thumshirn <jthumshirn@...e.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Praveen Murali <pmurali@...icube.com>,
        "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        chenxiang <chenxiang66@...ilicon.com>
Subject: Re: [PATCH] libsas: flush pending destruct work in
 sas_unregister_domain_devices()


On 2017/12/8 6:57, Cong Wang wrote:
> On Thu, Dec 7, 2017 at 5:37 AM, John Garry <john.garry@...wei.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.
>
> .
>

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