linux-kernel - Re: [PATCH v3 02/14] thermal: core: Rearrange checks in thermal_bind_cdev_to

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Message-ID: <CAJZ5v0jwkc2PB+osSkkYF9vJ1Vpp3MFE=cGQmQ2Xzjb3yjVfJg@mail.gmail.com>
Date: Wed, 21 Aug 2024 12:51:55 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: "lihuisong (C)" <lihuisong@...wei.com>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>, Linux PM <linux-pm@...r.kernel.org>, 
	LKML <linux-kernel@...r.kernel.org>, Daniel Lezcano <daniel.lezcano@...aro.org>, 
	Lukasz Luba <lukasz.luba@....com>, Zhang Rui <rui.zhang@...el.com>
Subject: Re: [PATCH v3 02/14] thermal: core: Rearrange checks in thermal_bind_cdev_to_trip()

On Wed, Aug 21, 2024 at 12:43 PM lihuisong (C) <lihuisong@...wei.com> wrote:
>
>
> 在 2024/8/19 23:51, Rafael J. Wysocki 写道:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >
> > It is not necessary to look up the thermal zone and the cooling device
> > in the respective global lists to check whether or not they are
> > registered.  It is sufficient to check whether or not their respective
> > list nodes are empty for this purpose.
> >
> > Use the above observation to simplify thermal_bind_cdev_to_trip().  In
> > addition, eliminate an unnecessary ternary operator from it.
> >
> > Moreover, add lockdep_assert_held() for thermal_list_lock to it because
> > that lock must be held by its callers when it is running.
> >
> > No intentional functional impact.
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > ---
> >
> > v1 -> v3: No changes
> >
> > ---
> >   drivers/thermal/thermal_core.c |   16 ++++------------
> >   1 file changed, 4 insertions(+), 12 deletions(-)
> >
> > Index: linux-pm/drivers/thermal/thermal_core.c
> > ===================================================================
> > --- linux-pm.orig/drivers/thermal/thermal_core.c
> > +++ linux-pm/drivers/thermal/thermal_core.c
> > @@ -781,25 +781,17 @@ int thermal_bind_cdev_to_trip(struct the
> >   {
> >       struct thermal_instance *dev;
> >       struct thermal_instance *pos;
> > -     struct thermal_zone_device *pos1;
> > -     struct thermal_cooling_device *pos2;
> >       bool upper_no_limit;
> >       int result;
> >
> > -     list_for_each_entry(pos1, &thermal_tz_list, node) {
> > -             if (pos1 == tz)
> > -                     break;
> > -     }
> > -     list_for_each_entry(pos2, &thermal_cdev_list, node) {
> > -             if (pos2 == cdev)
> > -                     break;
> > -     }
> > +     lockdep_assert_held(&thermal_list_lock);
> >
> > -     if (tz != pos1 || cdev != pos2)
> > +     if (list_empty(&tz->node) || list_empty(&cdev->node))
> The old verification is ensure that tz and cdev already add to
> thermal_tz_list and thermal_cdev_list，respectively.
> Namely, tz and cdev are definitely registered and intialized.
> The check is ok for all untizalized thermal_zone_device and cooling device.
> But the new verification doesn't seem to do that.

It doesn't need to do it and after this series it is only called from
thermal_zone_device_register_with_trips() and
__thermal_cooling_device_register() via thermal_zone_cdev_binding()
after both the cdev and the tz have been added to the list, under
thermal_list_lock.

I guess I can send a patch to remove the check altogether now.