linux-kernel - Re: [PATCH v3] driver core: fw_devlink: Stop trying to optimize cycle detection logic

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Message-ID: <CAGETcx8hZsm0qbwYDAeX_OztYs2jHPv9dc2ZajVivhEvQ7O6bg@mail.gmail.com>
Date: Tue, 19 Nov 2024 18:04:05 -0800
From: Saravana Kannan <saravanak@...gle.com>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	Francesco <francesco.dolcini@...adex.com>, 
	Tomi Valkeinen <tomi.valkeinen@...asonboard.com>, kernel-team@...roid.com, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] driver core: fw_devlink: Stop trying to optimize cycle
 detection logic

On Tue, Nov 19, 2024 at 5:40 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>
> Hi Saravana,
>
> On Wed, Oct 30, 2024 at 6:10 PM Saravana Kannan <saravanak@...gle.com> wrote:
> > In attempting to optimize fw_devlink runtime, I introduced numerous cycle
> > detection bugs by foregoing cycle detection logic under specific
> > conditions. Each fix has further narrowed the conditions for optimization.
> >
> > It's time to give up on these optimization attempts and just run the cycle
> > detection logic every time fw_devlink tries to create a device link.
> >
> > The specific bug report that triggered this fix involved a supplier fwnode
> > that never gets a device created for it. Instead, the supplier fwnode is
> > represented by the device that corresponds to an ancestor fwnode.
> >
> > In this case, fw_devlink didn't do any cycle detection because the cycle
> > detection logic is only run when a device link is created between the
> > devices that correspond to the actual consumer and supplier fwnodes.
> >
> > With this change, fw_devlink will run cycle detection logic even when
> > creating SYNC_STATE_ONLY proxy device links from a device that is an
> > ancestor of a consumer fwnode.
> >
> > Reported-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
> > Closes: https://lore.kernel.org/all/1a1ab663-d068-40fb-8c94-f0715403d276@ideasonboard.com/
> > Fixes: 6442d79d880c ("driver core: fw_devlink: Improve detection of overlapping cycles")
> > Tested-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
> > Signed-off-by: Saravana Kannan <saravanak@...gle.com>
>
> Thanks for your patch, which is now commit bac3b10b78e54b7d ("driver
> core: fw_devlink: Stop trying to optimize cycle detection logic") in
> next-20241107 and later.
>
> > Geert/Francesco,
> >
> > If you want to test this patch, pull it in and compare the output of
> > the following:
> >
> > ls -1 /sys/class/devlink
> >
> > The only device links that should be missing with the patch should be
> > device links in a cycle that weren't detected before.
>
> I gave it a try on all my boards, and compared the output on a few of
> them, and everything looks fine.

Thanks for testing the series Geert!

And no noticeable boot time increases?

Thanks,
Saravana