linux-kernel - Re: [PATCH 0/5]stop normal completion path entering a timeout req

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Message-ID: <20180621150143.GA26712@localhost.localdomain>
Date:   Thu, 21 Jun 2018 09:01:43 -0600
From:   Keith Busch <keith.busch@...el.com>
To:     "jianchao.wang" <jianchao.w.wang@...cle.com>
Cc:     Christoph Hellwig <hch@....de>, axboe@...nel.dk,
        martin.petersen@...cle.com, josef@...icpanda.com,
        ulf.hansson@...aro.org, linux-block@...r.kernel.org,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/5]stop normal completion path entering a timeout req

On Thu, Jun 21, 2018 at 09:13:30PM +0800, jianchao.wang wrote:
> Hi Christoph
> 
> On 06/21/2018 04:19 PM, Christoph Hellwig wrote:
> > On Thu, Jun 21, 2018 at 09:43:26AM +0800, jianchao.wang wrote:
> >> So we have to preserve the ability of block layer that it could prevent
> >> IO completion path from entering a timeout request.
> >>
> >> With scsi-debug module, I tried to simulate a scenario where timeout and IO
> >> completion path could occur concurrently, the system ran into crash easily.
> > 
> > Trace, please.  With the latest kernel.  I'm not saying that there
> > is nothing to fix, but the mode of never completing once timeout
> > requests as currently done is SCSI is clearly broken.
> > 
> 
> Sorry, I don't quite get your point.
> Do you mean we should do the modification in the scsi layer ?

I think it would just be helpful to start with the stack trace of your
observed crash + the reproduction steps so the problem (and hopefully
a solution) can be better understood.