Re: [PATCH bpf-next] bpf: Fix a typo in comment for DFS algorithm

[Xu Kuohai <xukuohai@huawei.com>]

On 10/26/2022 3:52 PM, Bagas Sanjaya wrote:
> On Tue, Oct 25, 2022 at 11:32:55PM -0700, Alexei Starovoitov wrote:
>> On Tue, Oct 25, 2022 at 7:42 PM Xu Kuohai <xukuohai@huaweicloud.com> wrote:
>>>
>>> From: Xu Kuohai <xukuohai@huawei.com>
>>>
>>> There is a typo in comment for DFS algorithm in bpf/verifier.c. The top
>>> element should not be popped until all its neighbors have been checked.
>>> Fix it.
>>>
>>> Fixes: 475fb78fbf48 ("bpf: verifier (add branch/goto checks)")
>>> Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
>>> ---
>>>   kernel/bpf/verifier.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
>>> index b83a8d420520..96ba5ea6d1a6 100644
>>> --- a/kernel/bpf/verifier.c
>>> +++ b/kernel/bpf/verifier.c
>>> @@ -10662,7 +10662,7 @@ static int check_return_code(struct bpf_verifier_env *env)
>>>    * 3      let S be a stack
>>>    * 4      S.push(v)
>>>    * 5      while S is not empty
>>> - * 6            t <- S.pop()
>>> + * 6            t <- S.top()
>>
>> Even with this fix the comment is not quite accurate.
>> I wonder whether we should keep it or delete it completely.
>> At least please use 'peek' instead of 'top'.
> 
> I think the comment should be in words (like other code comments in the
> kernel) instead.
> 

The beginning of the comment already says this is a piece of pseudo code. And
I don't think it's clearer to describe the algorithm in words than to describe
it in pseudo code.