linux-kernel - Re: [PATCH] libsas: flush pending destruct work in sas_unregister_domain

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Message-ID: <CAM_iQpV6XEHx5vrUz+2RVoBQQ_7hxkgasMcxiSWGBXHVDdwqKg@mail.gmail.com>
Date:   Thu, 7 Dec 2017 17:04:31 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     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>,
        Jason Yan <yanaijie@...wei.com>,
        chenxiang <chenxiang66@...ilicon.com>
Subject: Re: [PATCH] libsas: flush pending destruct work in sas_unregister_domain_devices()

On Thu, Dec 7, 2017 at 4:40 PM, Cong Wang <xiyou.wangcong@...il.com> wrote:
> On Thu, Dec 7, 2017 at 2:57 PM, Cong Wang <xiyou.wangcong@...il.com> 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.
>>
>
> I think we can just cancel the destruct work before calling
> sas_port_delete(). This should work even if it is called in
> another work.
>

This assumes sas_port_delete() could release resources recursively
in the hierarchy, this is true for sysfs but perhaps not true for other
resources...