linux-kernel - Re: [PATCH] driver core: shut down devices asynchronously

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Message-ID: <20230816195235.GA15421@wunner.de>
Date:   Wed, 16 Aug 2023 21:52:35 +0200
From:   Lukas Wunner <lukas@...ner.de>
To:     stuart hayes <stuart.w.hayes@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Tanjore Suresh <tansuresh@...gle.com>,
        Martin Belanger <Martin.Belanger@...l.com>,
        Oliver O'Halloran <oohall@...il.com>,
        Daniel Wagner <dwagner@...e.de>,
        Keith Busch <kbusch@...nel.org>
Subject: Re: [PATCH] driver core: shut down devices asynchronously

On Wed, Aug 16, 2023 at 02:42:26PM -0500, stuart hayes wrote:
> On 8/16/2023 10:54 AM, Lukas Wunner wrote:
> > Is there a particular reason why you're not using the infrastructure
> > provided by kernel/async.c and <async.h>, such as async_schedule()?
> > It wraps all the work_struct plumbing and also has helpers to await
> > completion.  I imagine using that might reduce LoC in this patch.
> 
> Not a good one.  Let me look into this, thank you.

A word of caution on async_synchronize_cookie(), it awaits the cookies
*before* the one you're passing into the function, so depending on the
use case it may be necessary to add + 1 to the cookie:

https://lore.kernel.org/intel-gfx/20160621075704.GB1821@nuc-i3427.alporthouse.com/

It's a nasty gotcha.  Just so you're aware of it. :)

Thanks,

Lukas