From: Christoph Hellwig <hch@lst.de>
To: Keith Busch <kbusch@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Keith Busch <kbusch@meta.com>,
linux-nvme@lists.infradead.org, sagi@grimberg.me,
Jens Axboe <axboe@kernel.dk>
Subject: Re: [PATCHv2] nvme-pci: fix timeout request state check
Date: Wed, 18 Jan 2023 08:33:30 +0100 [thread overview]
Message-ID: <20230118073330.GA27048@lst.de> (raw)
In-Reply-To: <Y8eJJ/9qo9c7jzLT@kbusch-mbp>
On Tue, Jan 17, 2023 at 10:52:39PM -0700, Keith Busch wrote:
> We're actually not batching here (no IOB in the timeout context), so we
> are either:
>
> a. calling nvme_pci_complete_rq() inline with the cqe
> b. racing with smp ipi or softirq
>
> If case (a), we will always see IDLE. If (b), we are racing and may see
> either COMPLETED or IDLE, so we have to check that it's not either of
> those. Since there's only one other state (STARTED) that was guaranteed
> prior to entering the timeout handler, we can just make sure it's not
> that one after the poll to know if abort escalation is needed.
The point is still that "started" is the wrong check here and relies
on an implementation detail. I think we're better off with an explicit
IDLE check and a big fat comment.
next prev parent reply other threads:[~2023-01-18 7:38 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-18 5:22 [PATCHv2] nvme-pci: fix timeout request state check Keith Busch
2023-01-18 5:33 ` Christoph Hellwig
2023-01-18 5:52 ` Keith Busch
2023-01-18 7:33 ` Christoph Hellwig [this message]
2023-01-18 15:21 ` Keith Busch
2023-01-18 16:35 ` Christoph Hellwig
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