On 2022/9/2 21:36, Petr Mladek wrote:
> On Fri 2022-09-02 09:28:59, Leizhen (ThunderTown) wrote:
>>>> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
>>>> index 42f7e716d56bf72..cb7abc821a50584 100644
>>>> --- a/kernel/livepatch/core.c
>>>> +++ b/kernel/livepatch/core.c
>>>> @@ -1041,9 +1041,9 @@ int klp_enable_patch(struct klp_patch *patch)
>>>> mutex_lock(&klp_mutex);
>>>>
>>>> if (!klp_is_patch_compatible(patch)) {
>>>> + mutex_unlock(&klp_mutex);
>>>> pr_err("Livepatch patch (%s) is not compatible with the already installed livepatches.\n",
>>>> patch->mod->name);
>>>> - mutex_unlock(&klp_mutex);
>>>
>>> I do not see how this change could reliably reduce the code size.
>>>
>>> As Joe wrote, it looks like a random effect that is specific to a
>>> particular compiler version, compilation options, and architecture.
>>>
>>> I am against these kind of random microptimizations. It is just a call
>>> for problems. If you move printk() outside of a lock, you need to make
>>> sure that the information is not racy.
>>
>> OK.
>>
>> mutex_lock(&klp_mutex);
>> if (!klp_is_patch_compatible(patch)) {
>> mutex_unlock(&klp_mutex);
>> <--------- Do you mean the incompatible patches maybe disabled at this point?
>
> This particular change is safe in the current design.
> klp_enable_patch() is called from the module_init() callback
> where patch->mod->name is defined. So it can't change.
>
> The problem is that it is not obvious that it is safe. One has to
> think about it. Also it might become dangerous when someone
> tries to call klp_enable_livepatch() for another livepatch module.
OK, I got it, thanks.
>
>> pr_err("Livepatch patch (%s) ...\n", patch->mod->name);
>> return -EINVAL;
>> }
>>
>>>
>>> It might be safe in this particular case. But it is a bad practice.
>>> It adds an extra work. It is error-prone with questionable gain.
>>>
>>> I am sorry but I NACK this patch. There must be better ways to
>>
>> OK
>
> Thanks for understanding.
>
> Best Regards,
> Petr
> .
>
--
Regards,
Zhen Lei
