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

[Xu Kuohai]

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@xxxxxxxxxxxxxxx> wrote:
> > > From: Xu Kuohai <xukuohai@xxxxxxxxxx>
> > >
> > > 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@xxxxxxxxxx>
> > > ---
> > >   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.