Re: [PATCH v3 02/14] thermal: core: Rearrange checks in thermal_bind_cdev_to_trip()

[lihuisong (C)]

在 2024/8/21 18:49, Daniel Lezcano 写道:
> On 21/08/2024 11:44, lihuisong (C) wrote:
> > 在 2024/8/21 17:28, Daniel Lezcano 写道:
> > > On 21/08/2024 10:49, lihuisong (C) wrote:
> > >
> > > [ ... ]
> > >
> > > > > -    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.
> > >
> > > If the tz or the cdev are registered then their "->node" is not 
> > > empty because they are linked with the thermal_list and cdev_list
> > >
> > > So either way is browsing the lists to find the tz/cdev or just 
> > > check "->node" is not empty. The latter the faster.
> > Assume that tz/cdev isn't intiazlized and registered to 
> > thermal_tz_list or thermal_cdev_list. And then directly call this 
> > interface.
>
> Then there is a bug in the internal code because the 
> thermal_zone_device_register*() and cooling_device_device_register() 
> allocate and initialize those structures.
>
> The caller of the function is supposed to use the API provided by the 
> thermal framework. It is not possible to plan every stupid things a 
> driver can do. In this particular case, very likely the kernel will 
> crash immediately which is a sufficient test for me and coercive 
> enough to have the API user to put its code in question ;)

A good point. Agree.