Messages in this thread | | | From | "Zhang, Rui" <> | Subject | Re: [PATCH 2/5] thermal/core: Reset cooling state during cooling device unregistration | Date | Tue, 28 Mar 2023 02:46:41 +0000 |
| |
On Mon, 2023-03-27 at 17:13 +0200, Rafael J. Wysocki wrote: > On Mon, Mar 27, 2023 at 4:50 PM Zhang, Rui <rui.zhang@intel.com> > wrote: > > On Fri, 2023-03-24 at 14:19 +0100, Rafael J. Wysocki wrote: > > > On Fri, Mar 24, 2023 at 8:08 AM Zhang Rui <rui.zhang@intel.com> > > > wrote: > > > > When unregistering a cooling device, it is possible that the > > > > cooling > > > > device has been activated. And once the cooling device is > > > > unregistered, > > > > no one will deactivate it anymore. > > > > > > > > Reset cooling state during cooling device unregistration. > > > > > > > > Signed-off-by: Zhang Rui <rui.zhang@intel.com> > > > > --- > > > > In theory, this problem that this patch fixes can be triggered > > > > on a > > > > platform with ACPI Active cooling, by > > > > 1. overheat the system to trigger ACPI active cooling > > > > 2. unload ACPI fan driver > > > > 3. check if the fan is still spinning > > > > But I don't have such a system so I didn't trigger then problem > > > > and > > > > I > > > > only did build & boot test. > > > > > > So I'm not sure if this change is actually safe. > > > > > > In the example above, the system will still need the fan to spin > > > after > > > the ACPI fan driver is unloaded in order to cool down, won't it? > > > > Then we can argue that the ACPI fan driver should not be unloaded > > in > > this case. > > I don't think that whether or not the driver is expected to be > unloaded at a given time has any bearing on how it should behave when > actually unloaded. > > Leaving the cooling device in its current state is "safe" from the > thermal control perspective, but it may affect the general user > experience (which may include performance too) going forward, so > there > is a tradeoff.
Right. If we don't have a third choice, then the question is simple. "thermal safety" vs. "user experience"?
I'd vote for "thermal safety" and drop this patch series. > > What do the other cooling device drivers do in general when they get > removed?
No cooling device driver has extra handling after cdev unregistration.
thanks, rui
| |