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Date: Tue, 3 Feb 2015 08:28:19 +0800
Message-ID: <CA+eFSM3-Xw1sqN0sCx4LHXYH7d81j+qtx_z6VZ_6QXc7uu2QyA@mail.gmail.com>
Subject: Re: General protection fault in iscsi_rx_thread_pre_handler
From: Gavin Guo <gavin.guo@canonical.com>
To: "Nicholas A. Bellinger" <nab@linux-iscsi.org>
Cc: linux-scsi@vger.kernel.org, target-devel@vger.kernel.org,
        linux-kernel <linux-kernel@vger.kernel.org>
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Hi Nicholas,

On Sun, Feb 1, 2015 at 11:47 AM, Gavin Guo <gavin.guo@canonical.com> wrote:
> Hi Nicholas,
>
> On Sat, Jan 31, 2015 at 6:53 AM, Nicholas A. Bellinger
> <nab@linux-iscsi.org> wrote:
>> On Fri, 2015-01-23 at 09:30 +0800, Gavin Guo wrote:
>>> Hi Nicholas,
>>>
>>> On Fri, Jan 23, 2015 at 1:35 AM, Nicholas A. Bellinger
>>> <nab@linux-iscsi.org> wrote:
>>> > On Thu, 2015-01-22 at 23:56 +0800, Gavin Guo wrote:
>>> >> Hi Nicolas,
>>> >>
>>> >> On Thu, Jan 22, 2015 at 5:50 PM, Nicholas A. Bellinger
>>> >> <nab@linux-iscsi.org> wrote:
>>> >> > Hi Gavin,
>>> >> >
>>> >> > On Thu, 2015-01-22 at 06:38 +0800, Gavin Guo wrote:
>>> >> >> Hi all,
>>> >> >>
>>> >> >> The general protection fault screenshot is attached.
>>> >> >>
>>> >> >> Summary:
>>> >> >> The kernel is Ubuntu-3.13.0-39.66. I've done basic analysis and found
>>> >> >> the fault is in list_del of iscsi_del_ts_from_active_list. And it
>>> >> >> looks like deleting the iscsi_thread_set *ts two times. The point to
>>> >> >> delete including iscsi_get_ts_from_inactive_list, was also checked but
>>> >> >> still can't find the clue. Really appreciate if anyone can provide any
>>> >> >> idea on the bug.
>>> >> >>
>>> >
>>> > <SNIP>
>>> >
>>> >> >
>>> >> > Thanks for your detailed analysis.
>>> >> >
>>> >> > A similar bug was reported off-list some months back by a person using
>>> >> > iser-target + RoCE export on v3.12.y code.  Just to confirm, your
>>> >> > environment is using traditional iscsi-target + TCP export, right..?
>>> >>
>>> >> I am sorry that I'm not an expert of the field and already google RoCE
>>> >> on the internet but still don't really know what RoCE is. However, I
>>> >> can provide the informations.  We used iscsiadm on the initiator side
>>> >> and lio_node and tcm_node commands to create the targets for
>>> >> connection. I think it should be normal  iscsi-target using TCP
>>> >> export.
>>> >>
>>> >
>>> > Yep, that would be traditional iscsi-target + TCP export.
>>> >
>>> >> >
>>> >> > At the time, a different set of iser-target related changes ended up
>>> >> > avoiding this issue on his particular setup, so we thought it was likely
>>> >> > a race triggered by login failures specific to iser-target code.
>>> >> >
>>> >> > There was a untested patch (included inline below) to drop the legacy
>>> >> > active_ts_list usage all-together, but IIRC he was not able to reproduce
>>> >> > further so the patch didn't get picked up for mainline.
>>> >> >
>>> >> > If your able to reliability reproduce, please try with the following
>>> >> > patch and let us know your progress.
>>> >>
>>> >> Thanks for your time reading the mail. I'll let you know the result.
>>> >
>>> > Just curious, are you able to reliability reproduce this bug in a VM..?
>>>
>>> Thanks for your caring, the machine is on the customer side, I've
>>> asked and now waiting for their response.
>>
>> Hi Gavin,
>>
>> Just curious if there has been any update on this yet..?
>>
>> --nab
>>
>
> Really thanks for your attention. I'm also currently waiting for the
> customer's reply and will send the email again to ask for the result.
> However, I think the symptom may be hard to replicate that's why the
> customer didn't reply me for a long time. Thanks for your time again.
>
> Thanks,
> Gavin

Sorry for making you wait so long. I just got the response from the
customer, they said the general protection fault happened just 2 times
in the past and cannot be reliably reproduced. And I am now waiting
for the verification test.

Thanks,
Gavin
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