linux-kernel - Re: [PATCH v3 05/14] thermal: core: Move thermal zone locking out of bind/unbind functions

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Message-ID: <CAJZ5v0gci_a23e=siMWRQGHAUiiHDUtPgZtWWfNW066ENdv5tw@mail.gmail.com>
Date: Wed, 21 Aug 2024 12:30:17 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: "lihuisong (C)" <lihuisong@...wei.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, "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 05/14] thermal: core: Move thermal zone locking out of
 bind/unbind functions

On Wed, Aug 21, 2024 at 11:02 AM lihuisong (C) <lihuisong@...wei.com> wrote:
>
>
> 在 2024/8/20 18:27, Rafael J. Wysocki 写道:
> > On Tue, Aug 20, 2024 at 10:27 AM lihuisong (C) <lihuisong@...wei.com> wrote:
> >>
> >> 在 2024/8/19 23:58, Rafael J. Wysocki 写道:
> >>> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >>>
> >>> Since thermal_bind_cdev_to_trip() and thermal_unbind_cdev_from_trip()
> >>> acquire the thermal zone lock, the locking rules for their callers get
> >>> complicated.  In particular, the thermal zone lock cannot be acquired
> >>> in any code path leading to one of these functions even though it might
> >>> be useful to do so.
> >>>
> >>> To address this, remove the thermal zone locking from both these
> >>> functions, add lockdep assertions for the thermal zone lock to both
> >>> of them and make their callers acquire the thermal zone lock instead.
> >>>
> >>> No intentional functional impact.
> >>>
> >>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >>> ---
> >>>
> >>> v2 -> v3: Rebase after dropping patches [04-05/17] from the series
> >>>
> >>> v1 -> v2: No changes
> >>>
> >>> ---
> >>>    drivers/acpi/thermal.c         |    2 +-
> >>>    drivers/thermal/thermal_core.c |   30 ++++++++++++++++++++++--------
> >>>    2 files changed, 23 insertions(+), 9 deletions(-)
> >>>
> >>> Index: linux-pm/drivers/thermal/thermal_core.c
> >>> ===================================================================
> >>> --- linux-pm.orig/drivers/thermal/thermal_core.c
> >>> +++ linux-pm/drivers/thermal/thermal_core.c
> >>> @@ -785,6 +785,7 @@ int thermal_bind_cdev_to_trip(struct the
> >>>        int result;
> >>>
> >> <snip>
> >>> Index: linux-pm/drivers/acpi/thermal.c
> >>> ===================================================================
> >>> --- linux-pm.orig/drivers/acpi/thermal.c
> >>> +++ linux-pm/drivers/acpi/thermal.c
> >>> @@ -609,7 +609,7 @@ static int acpi_thermal_bind_unbind_cdev
> >>>                .thermal = thermal, .cdev = cdev, .bind = bind
> >>>        };
> >>>
> >>> -     return for_each_thermal_trip(thermal, bind_unbind_cdev_cb, &bd);
> >>> +     return thermal_zone_for_each_trip(thermal, bind_unbind_cdev_cb, &bd);
> >> If so, it seems that the for_each_thermal_trip() can be removed or no
> >> need to export.
> > I beg to differ:
> >
> > $ git grep for_each_thermal_trip | head -1
> > drivers/net/wireless/intel/iwlwifi/mvm/tt.c:
> > for_each_thermal_trip(mvm->tz_device.tzone, iwl_trip_temp_cb, &twd);
> Can we modify it for tt.c?

Not really.

tt.c invokes this under the thermal zone lock, so it cannot use the
"locked" variant.

> It doesn't seem to keep two interfaces. I'm a little confused for that.

The difference between for_each_thermal_trip() and
thermal_zone_for_each_trip() is "unlocked" vs "locked", respectively.
It may just be a question of naming ...