Re: [PATCH bpf-next v3 3/5] bpf: Free element after unlock in __htab_map_lookup_and_delete_elem()

["Toke Høiland-Jørgensen" <toke@kernel.org>]

Hou Tao <houtao@huaweicloud.com> writes:

> Hi,
>
> On 1/17/2025 8:35 PM, Toke Høiland-Jørgensen wrote:
>> Hou Tao <houtao@huaweicloud.com> writes:
>>
>>> From: Hou Tao <houtao1@huawei.com>
>>>
>>> The freeing of special fields in map value may acquire a spin-lock
>>> (e.g., the freeing of bpf_timer), however, the lookup_and_delete_elem
>>> procedure has already held a raw-spin-lock, which violates the lockdep
>>> rule.
>> This implies that we're fixing a locking violation here? Does this need
>> a Fixes tag?
>>
>> -Toke
>
> Ah, the fix tag is a bit hard. The lockdep violation in the patch is
> also related with PREEMPT_RT, however, the lookup_and_delete_elem is
> introduced in v5.14. Also considering that patch #4 will also fix the
> lockdep violation in the case, I prefer to not add a fix tag in the
> patch. Instead I will update the commit message for the patch to state
> that it will reduce the lock scope of bucket lock. What do you think ?

Sure; and maybe put the same explanation for why there's no Fixes tag
into the commit message as well? :)

-Toke