linux-kernel - Re: [RFC PATCH v3 00/19] scsi: scsi_error: Introduce new error handle mechanism

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Message-ID: <fc08e3a1-da7f-4eb0-a738-cf6b6958316b@acm.org>
Date: Fri, 14 Mar 2025 08:55:25 -0700
From: Bart Van Assche <bvanassche@....org>
To: Hannes Reinecke <hare@...e.de>, JiangJianJun <jiangjianjun3@...wei.com>,
 jejb@...ux.ibm.com, martin.petersen@...cle.com, linux-scsi@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, lixiaokeng@...wei.com,
 hewenliang4@...wei.com, yangkunlin7@...wei.com
Subject: Re: [RFC PATCH v3 00/19] scsi: scsi_error: Introduce new error handle
 mechanism

On 3/14/25 2:01 AM, Hannes Reinecke wrote:
> 3. The current EH framework is designed around 'struct scsi_cmnd'.
> Which means that the command _initiating_ the error handling can
> only be returned once the _entire_ error handling (with all
> escalations) is finished. And more often than not, the application
> is waiting on that command to be completed before the next I/O
> is sent. And that really limits the effectiveness of any improved
> error handler; the application ultimatively has to wait for a
> host reset before it can contine.
> 
> But anyway.
> We already have a mechanism for asynchronous command aborts;
> have you checked if you can adapt if for LUN reset, too?
> That would be the easiest solution, I guess ...

Hmm ... does this mean submitting a LUN reset while concurrently new
SCSI commands can be submitted from another thread? I don't think that's
safe.

Additionally, how could a LUN reset help if a SCSI abort doesn't help?
If a SCSI abort doesn't help, it probably means that the host controller
locked up, e.g. due to a firmware bug. How to recover from this without
resetting the host controller?

Thanks,

Bart.