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 <YkO7d7Eel4BVQOy4@kbusch-mbp.dhcp.thefacebook.com> <20220330062516.GA24340@wunner.de>
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From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Wed, 30 Mar 2022 13:13:30 +0200
Message-ID: <CAJZ5v0jUuv7+j5M7xKhC2BdNdj-t==f56GbSDK_Tfrr7=pMcLQ@mail.gmail.com>
Subject: Re: [PATCH v1 0/3] Asynchronous shutdown interface and example implementation
To:     Lukas Wunner <lukas@wunner.de>
Cc:     Keith Busch <kbusch@kernel.org>,
        Tanjore Suresh <tansuresh@google.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J . Wysocki" <rafael@kernel.org>,
        Christoph Hellwig <hch@lst.de>,
        Sagi Grimberg <sagi@grimberg.me>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-nvme <linux-nvme@lists.infradead.org>,
        Linux PCI <linux-pci@vger.kernel.org>
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On Wed, Mar 30, 2022 at 8:25 AM Lukas Wunner <lukas@wunner.de> wrote:
>
> On Tue, Mar 29, 2022 at 08:07:51PM -0600, Keith Busch wrote:
> > Thanks, I agree we should improve shutdown times. I tried a while ago, but
> > lost track to follow up at the time. Here's the reference, fwiw, though it
> > may be out of date :):
> >
> >   http://lists.infradead.org/pipermail/linux-nvme/2014-May/000826.html
> >
> > The above solution is similiar to how probe waits on an async domain.
> > Maybe pci can schedule the async shutdown instead of relying on low-level
> > drivers so that everyone implicitly benefits instead of just nvme? I'll
> > double-check if that's reasonable, but I'll look through this series too.
>
> Using the async API seems much more reasonable than adding new callbacks.
>
> However I'd argue that it shouldn't be necessary to amend any drivers,
> this should all be doable in the driver core:  Basically a device needs
> to wait for its children and device links consumers to shutdown, apart
> from that everything should be able to run asynchronously.

Well, this is done already in the system-wide and hibernation paths.
It should be possible to implement asynchronous shutdown analogously.