linux-kernel - Re: [PATCH] PM: domains: Shrink locking area of the gpd_list

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Date:   Thu, 24 Jun 2021 13:33:59 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH] PM: domains: Shrink locking area of the gpd_list_lock

Quoting Ulf Hansson (2021-06-23 02:55:24)
> On Wed, 23 Jun 2021 at 10:31, Stephen Boyd <swboyd@...omium.org> wrote:
> > lock as far down as possible to fix the problem, which is holding it
> > over the calls into OPP.
>
> Yes, we don't want that.
>
> >
> > If I've read the code correctly it serves no purpose to grab the
> > gpd_list_lock here in genpd_add_provider() because we grab the
> > of_genpd_mutex and that is protecting the of_genpd_providers list
> > everywhere else. Is that right? Put another way, This hunk of the patch
> > can be dropped and then your concern will be addressed and there isn't
> > anything more to do.
>
> It certainly can be dropped from the $subject patch, please re-spin to
> update that.
>
> However, there are additional changes that deserve to be done to
> improve the behaviour around the locks. More precisely, the
> &gpd_list_lock and the &of_genpd_mutex should be completely decoupled,
> but there are some other related things as well.
>
> Probably it's easier if I post a patch, on top of yours, to try to
> further improve the behavior. I would appreciate it if you could help
> with the test/review then.

Sure no problem. I've sent v2 with this hunk dropped. I can test your
followup.