On 4/4/24 11:17, Petr Mladek wrote:
> On Tue 2024-04-02 09:52:31, Joe Lawrence wrote:
>> On Tue, Apr 02, 2024 at 11:09:54AM +0800, zhangwarden@xxxxxxxxx wrote:
>>> From: Wardenjohn <zhangwarden@xxxxxxxxx>
>>>
>>> In livepatch, using KLP_UNDEFINED is seems to be confused.
>>> When kernel is ready, livepatch is ready too, which state is
>>> idle but not undefined. What's more, if one livepatch process
>>> is finished, the klp state should be idle rather than undefined.
>>>
>>> Therefore, using KLP_IDLE to replace KLP_UNDEFINED is much better
>>> in reading and understanding.
>>> ---
>>> include/linux/livepatch.h | 1 +
>>> kernel/livepatch/patch.c | 2 +-
>>> kernel/livepatch/transition.c | 24 ++++++++++++------------
>>> 3 files changed, 14 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
>>> index 9b9b38e89563..c1c53cd5b227 100644
>>> --- a/include/linux/livepatch.h
>>> +++ b/include/linux/livepatch.h
>>> @@ -19,6 +19,7 @@
>>>
>>> /* task patch states */
>>> #define KLP_UNDEFINED -1
>>> +#define KLP_IDLE -1
>>
>> Hi Wardenjohn,
>>
>> Quick question, does this patch intend to:
>>
>> - Completely replace KLP_UNDEFINED with KLP_IDLE
>> - Introduce KLP_IDLE as an added, fourth potential state
>> - Introduce KLP_IDLE as synonym of sorts for KLP_UNDEFINED under certain
>> conditions
>>
>> I ask because this patch leaves KLP_UNDEFINED defined and used in other
>> parts of the tree (ie, init/init_task.c), yet KLP_IDLE is added and
>> continues to use the same -1 enumeration.
>
> Having two names for the same state adds more harm than good.
>
> Honestly, neither "task->patch_state == KLP_UNDEFINED" nor "KLP_IDLE"
> make much sense.
>
> The problem is in the variable name. It is not a state of a patch.
> It is the state of the transition. The right solution would be
> something like:
>
> klp_target_state -> klp_transition_target_state
> task->patch_state -> task->klp_transition_state
> KLP_UNKNOWN -> KLP_IDLE
>
Yes, this is exactly how I think of these when reading the code. The
model starts to make a lot more sense once you look at it thru this lens :)
> But it would also require renaming:
>
> /proc/<pid>/patch_state -> klp_transition_state
>
> which might break userspace tools => likely not acceptable.
>
>
> My opinion:
>
> It would be nice to clean this up but it does not look worth the
> effort.
>
Agreed. Instead of changing code and the sysfs interface, we could
still add comments like:
/* task patch transition target states */
#define KLP_UNDEFINED -1 /* idle, no transition in progress */
#define KLP_UNPATCHED 0 /* transitioning to unpatched state */
#define KLP_PATCHED 1 /* transitioning to patched state */
/* klp transition target state */
static int klp_target_state = KLP_UNDEFINED;
struct task_struct = {
.patch_state = KLP_UNDEFINED, /* klp transition state */
Maybe just one comment is enough? Alternatively, we could elaborate in
Documentation/livepatch/livepatch.rst if it's really confusing.
Wardenjohn, since you're probably reading this code with fresh(er) eyes,
would any of the above be helpful?
--
Joe
