[PATCH] ACPI: Remove possible recursion from thermal driver

[PATCH] ACPI: Remove possible recursion from thermal driver

[Alexey Starikovskiy]

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Hi,

This patch helps to fight infinite recursion on some ACER laptops, see
bugzilla #8385.

Thanks,
Alex.

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Thermal check may result in thermal points to be moved down. Don't do thermal check again in this case.

From: Alexey Starikovskiy <aystarik@gmail.com>

Signed-off-by: Alexey Starikovskiy <aystarik@gmail.com>
---

 drivers/acpi/thermal.c |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)

diff --git a/drivers/acpi/thermal.c b/drivers/acpi/thermal.c
index 1ada017..7aa5f11 100644
--- a/drivers/acpi/thermal.c
+++ b/drivers/acpi/thermal.c
@@ -1106,7 +1106,6 @@ static void acpi_thermal_notify(acpi_handle handle, u32 event, void *data)
 		break;
 	case ACPI_THERMAL_NOTIFY_THRESHOLDS:
 		acpi_thermal_get_trip_points(tz);
-		acpi_thermal_check(tz);
 		acpi_bus_generate_event(device, event, 0);
 		break;
 	case ACPI_THERMAL_NOTIFY_DEVICES:

Re: [PATCH] ACPI: Remove possible recursion from thermal driver

[Len Brown]

> --- a/drivers/acpi/thermal.c
> +++ b/drivers/acpi/thermal.c
> @@ -1106,7 +1106,6 @@ static void acpi_thermal_notify(acpi_handle handle, u32 event, void *data)
> 		break;
> 	case ACPI_THERMAL_NOTIFY_THRESHOLDS:
> 		acpi_thermal_get_trip_points(tz);
>-		acpi_thermal_check(tz);
> 		acpi_bus_generate_event(device, event, 0);
> 		break;
> 	case ACPI_THERMAL_NOTIFY_DEVICES:

I don't think we can do this.
When the thresholds change, there must be a check to compare the temperature
with the thresholds -- otherwise what good was it to change the thresholds?

-Len

Re: [PATCH] ACPI: Remove possible recursion from thermal driver

[Alexey Starikovskiy]

Please read the spec 11.1.2 and 11.1.2.3. Trip points change _only_ to
create a hysteresis loop, not by themselves. This means that we will
get 0x81 type _only_ in response to us changing active state, the
moment then we have temperature and just decided to move away from
this trip point, not closer to it.
If the temperature change, we get another event, 0x80, and _then_ we
do thermal_check()...

Regards,
Alex.


On 5/16/07, Len Brown <lenb@kernel.org> wrote:
>
> > --- a/drivers/acpi/thermal.c
> > +++ b/drivers/acpi/thermal.c
> > @@ -1106,7 +1106,6 @@ static void acpi_thermal_notify(acpi_handle handle, u32 event, void *data)
> >               break;
> >       case ACPI_THERMAL_NOTIFY_THRESHOLDS:
> >               acpi_thermal_get_trip_points(tz);
> >-              acpi_thermal_check(tz);
> >               acpi_bus_generate_event(device, event, 0);
> >               break;
> >       case ACPI_THERMAL_NOTIFY_DEVICES:
>
> I don't think we can do this.
> When the thresholds change, there must be a check to compare the temperature
> with the thresholds -- otherwise what good was it to change the thresholds?
>
> -Len
>

Re: [PATCH] ACPI: Remove possible recursion from thermal driver

[Len Brown]

On Tuesday 15 May 2007 22:19, Alexey Starikovskiy wrote:
> Please read the spec 11.1.2 and 11.1.2.3. Trip points change _only_ to
> create a hysteresis loop, not by themselves. This means that we will
> get 0x81 type _only_ in response to us changing active state, the
> moment then we have temperature and just decided to move away from
> this trip point, not closer to it.
> If the temperature change, we get another event, 0x80, and _then_ we
> do thermal_check()...
> 

Hmm, this sounds promising.
Bob and I discussed this a few weeks ago and for some reason
we were convinced that we needed to get the temperature and
compare it to the new trip points.  Maybe we were wrong.

-Len

> 
> On 5/16/07, Len Brown <lenb@kernel.org> wrote:
> >
> > > --- a/drivers/acpi/thermal.c
> > > +++ b/drivers/acpi/thermal.c
> > > @@ -1106,7 +1106,6 @@ static void acpi_thermal_notify(acpi_handle handle, u32 event, void *data)
> > >               break;
> > >       case ACPI_THERMAL_NOTIFY_THRESHOLDS:
> > >               acpi_thermal_get_trip_points(tz);
> > >-              acpi_thermal_check(tz);
> > >               acpi_bus_generate_event(device, event, 0);
> > >               break;
> > >       case ACPI_THERMAL_NOTIFY_DEVICES:
> >
> > I don't think we can do this.
> > When the thresholds change, there must be a check to compare the temperature
> > with the thresholds -- otherwise what good was it to change the thresholds?
> >
> > -Len
> >
>