linux-kernel - Re: [PATCH v2 6/7] nvme-pci: add device coredump support

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Date:   Wed, 08 May 2019 09:25:34 +0900
From:   Minwoo Im <minwoo.im@...sung.com>
To:     Keith Busch <kbusch@...nel.org>,
        Akinobu Mita <akinobu.mita@...il.com>,
        Minwoo Im <minwoo.im@...sung.com>
CC:     Jens Axboe <axboe@...com>, Sagi Grimberg <sagi@...mberg.me>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
        Keith Busch <keith.busch@...el.com>,
        Minwoo Im <minwoo.im.dev@...il.com>,
        Johannes Berg <johannes@...solutions.net>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v2 6/7] nvme-pci: add device coredump support

> This is a bit of a mine field. The shutdown_lock is held when reclaiming
> requests that didn't see a response. If you're holding it here and your
> telemetry log page times out, we're going to deadlock. And since the
> controller is probably in a buggered state when you try to retrieve one,
> I would guess an unrecoverable timeout is the most likely outcome.

Akinobu,

I actually agree with Keith's one.  In my experience, there was always internal
error inside device when timeout occurs in nvme driver which means the
following command might not be completed due to lack of response from
device.