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

lihuisong (C)
2024-08-21T11:22:58Z

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.