From: wangyijing <wangyijing@huawei.com>
To: John Garry <john.garry@huawei.com>,
Dan Williams <dan.j.williams@intel.com>
Cc: <jejb@linux.vnet.ibm.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
linux-scsi <linux-scsi@vger.kernel.org>,
<john.garry2@mail.dcu.ie>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
<linuxarm@huawei.com>, <lindar_liu@usish.com>,
Tejun Heo <tj@kernel.org>, <jinpu.wang@profitbricks.com>
Subject: Re: [RFC PATCH] scsi: libsas: fix WARN on device removal
Date: Fri, 11 Nov 2016 16:12:02 +0800 [thread overview]
Message-ID: <58257D52.6090507@huawei.com> (raw)
In-Reply-To: <9870e7bc-a472-1913-1930-ac022e8ad5e8@huawei.com>
>
> They're not the same. I don't see how your solution properly deals with remote sas_port deletion.
>
> When we unplug a device connected to an expander, can't the sas_port be deleted twice, in sas_unregister_devs_sas_addr() from domain revalidation and also now in sas_destruct_devices()? I think that this gives a NULL dereference.
> And we still get the WARN as the sas_port has still been deleted before the device.
>
> In my solution, we should always delete the sas_port after the attached device.
>
>>>
>>> i.e. it moves the port destruction to the workqueue and still suffers
>>> from the flutter problem:
>>>
>>> http://marc.info/?l=linux-scsi&m=143801026028006&w=2
>>> http://marc.info/?l=linux-scsi&m=143801971131073&w=2
>>>
>>> Perhaps we instead need to quiet this warning?
>>>
>>> http://marc.info/?l=linux-scsi&m=143802229932175&w=2
>
> I have not seen the flutter issue. I am just trying to solve the horrible WARN dump.
> However I do understand that there may be a issue related to how we queue the events; there was a recent attempt to fix this, but it came to nothing:
> https://www.spinics.net/lists/linux-scsi/msg99991.html
We found libsas hotplug several problems:
1. sysfs warning calltrace(like the case you found);
2. hot-add and hot-remove work events may process out of order;
3. in some extreme cases, libsas may miss some events, if the same event is still pending in workqueue.
It's a complex issue, we posted two patches, try to fix these issues, but now few people are interested in it :(
>
> Cheers,
> John
>
>>
>> Alternatively we need a mechanism to cancel in-flight port shutdown
>> requests when we start re-attaching devices before queued port
>> destruction events have run.
>>
>> .
>>
>
>
> _______________________________________________
> linuxarm mailing list
> linuxarm@huawei.com
> http://rnd-openeuler.huawei.com/mailman/listinfo/linuxarm
>
> .
>
next prev parent reply other threads:[~2016-11-11 8:20 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-03 14:58 [RFC PATCH] scsi: libsas: fix WARN on device removal John Garry
2016-11-09 12:28 ` John Garry
2016-11-09 17:36 ` John Garry
2016-11-09 19:09 ` Dan Williams
2016-11-09 20:35 ` Dan Williams
2016-11-10 11:53 ` John Garry
2016-11-11 8:12 ` wangyijing [this message]
2016-11-11 8:23 ` John Garry
2016-11-11 8:49 ` wangyijing
2016-11-17 15:23 ` John Garry
2016-11-18 1:51 ` Martin K. Petersen
2016-11-18 1:53 ` Dan Williams
2016-11-18 9:00 ` John Garry
2016-11-18 19:08 ` Dan Williams
2016-11-21 15:16 ` John Garry
2016-11-21 17:13 ` Dan Williams
2016-11-22 16:56 ` John Garry
2016-11-23 1:07 ` wangyijing
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