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SubjectRe: [External] Re: [PATCH v3] livepatch: Don't block removal of patches that are safe to unload
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On 2022/3/16 11:01 下午, Petr Mladek wrote:
> On Wed 2022-03-16 15:48:25, Miroslav Benes wrote:
>> On Sat, 12 Mar 2022, Chengming Zhou wrote:
>>
>>> module_put() is not called for a patch with "forced" flag. It should
>>> block the removal of the livepatch module when the code might still
>>> be in use after forced transition.
>>>
>>> klp_force_transition() currently sets "forced" flag for all patches on
>>> the list.
>>>
>>> In fact, any patch can be safely unloaded when it passed through
>>> the consistency model in KLP_UNPATCHED transition.
>>>
>>> By other words, the "forced" flag must be set only for livepatches
>>
>> s/By/In/
>>
>>> that are being removed. In particular, set the "forced" flag:
>>>
>>> + only for klp_transition_patch when the transition to KLP_UNPATCHED
>>> state was forced.
>>>
>>> + all replaced patches when the transition to KLP_PATCHED state was
>>> forced and the patch was replacing the existing patches.
>>>
>>> index 5683ac0d2566..7f25a5ae89f6 100644
>>> --- a/kernel/livepatch/transition.c
>>> +++ b/kernel/livepatch/transition.c
>>> @@ -641,6 +641,18 @@ void klp_force_transition(void)
>>> for_each_possible_cpu(cpu)
>>> klp_update_patch_state(idle_task(cpu));
>>>
>>> - klp_for_each_patch(patch)
>>> - patch->forced = true;
>>> + /*
>>> + * Only need to set forced flag for the transition patch
>>> + * when force transition to KLP_UNPATCHED state, but
>>> + * have to set forced flag for all replaced patches
>>> + * when force atomic replace transition.
>>> + */
>>
>> How about something like
>>
>> /*
>> * Set forced flag for patches being removed, which is the transition
>> * patch in KLP_UNPATCHED state or all replaced patches when forcing
>> * the atomic replace transition.
>> */
>
> Or just the first sentence:
>
> /* Set forced flag for patches being removed */
>
> The rest is visible from the code.
>
> Either version works for me. If we agree on it then I update
> the text when pushing the patch.

Ok, this works for me too ;-)

Thanks.

>
> Best Regards,
> Petr

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