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 1/20/2025 4:52 PM, Toke Høiland-Jørgensen wrote:
>> 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? :)
>
> I have rewritten the commit message for the patch and it is ready for
> resend. However it seems Alexei has already merged this patch set [1],
> therefore, I will keep it as is.

Ah well; thanks anyway! :)

-Toke