linux-kernel - Re: [PATCH v10 0/5] shut down devices asynchronously

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Message-ID: <aGaklKejxefXTQB4@jeremy-HP-Z840-Workstation>
Date: Thu, 3 Jul 2025 08:41:08 -0700
From: Jeremy Allison <jra@...ba.org>
To: Christoph Hellwig <hch@....de>
Cc: Stuart Hayes <stuart.w.hayes@...il.com>, linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Martin Belanger <Martin.Belanger@...l.com>,
	Oliver O'Halloran <oohall@...il.com>,
	Daniel Wagner <dwagner@...e.de>, Keith Busch <kbusch@...nel.org>,
	Lukas Wunner <lukas@...ner.de>, David Jeffery <djeffery@...hat.com>,
	Jeremy Allison <jallison@....com>, Jens Axboe <axboe@...com>,
	Sagi Grimberg <sagi@...mberg.me>, linux-nvme@...ts.infradead.org,
	Nathan Chancellor <nathan@...nel.org>,
	Jan Kiszka <jan.kiszka@...mens.com>,
	Bert Karwatzki <spasswolf@....de>, sultan@...neltoast.com,
	jra@...ba.org
Subject: Re: [PATCH v10 0/5] shut down devices asynchronously

On Thu, Jul 03, 2025 at 01:46:56PM +0200, Christoph Hellwig wrote:
>On Wed, Jun 25, 2025 at 03:18:48PM -0500, Stuart Hayes wrote:
>> Address resource and timing issues when spawning a unique async thread
>> for every device during shutdown:
>>   * Make the asynchronous threads able to shut down multiple devices,
>>     instead of spawning a unique thread for every device.
>>   * Modify core kernel async code with a custom wake function so it
>>     doesn't wake up threads waiting to synchronize every time the cookie
>>     changes
>
>Given all these thread spawning issues, why can't we just go back
>to the approach that kicks off shutdown asynchronously and then waits
>for it without spawning all these threads?

It isn't just an nvme issue. Red Hat found the same issue
with SCSI devices.

My colleague Sultan Alsawaf posted a simpler fix for the
earlier patch here:

https://lists.infradead.org/pipermail/linux-nvme/2025-January/053666.html

Maybe this could be explored.