linux-kernel - Re: [PATCH v2] coccinelle: semantic code search for missingof_node

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Date:   Fri, 5 Jul 2019 07:29:49 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...6.fr>
To:     wen.yang99@....com.cn
cc:     Markus.Elfring@....de, linux-kernel@...r.kernel.org,
        wang.yi59@....com.cn, Gilles Muller <Gilles.Muller@...6.fr>,
        nicolas.palix@...g.fr, michal.lkml@...kovi.net,
        yamada.masahiro@...ionext.com, cocci@...teme.lip6.fr
Subject: Re: [PATCH v2] coccinelle: semantic code search for
 missingof_node_put



On Thu, 4 Jul 2019, wen.yang99@....com.cn wrote:

> > > > +x = @p1\(of_find_all_nodes\|
> > >
> > > I would find this SmPL disjunction easier to read without the usage
> > > of extra backslashes.
> > >
> > > +x =
> > > +(of_…
> > > +|of_…
> > > +)@p1(...);
> >
> > Did you actually test this?  I doubt that a position metavariable can be
> > put on a ) of a disjunction.
> >
> > > > +|
> > > > +return x;
> > > > +|
> > > > +return of_fwnode_handle(x);
> > >
> > > Can a nested SmPL disjunction be helpful at such places?
> > >
> > > +|return
> > > +(x
> > > +|of_fwnode_handle(x)
> > > +);
> >
> > The original code is much more readable.  The internal representation will
> > be the same.
> >
> > > > +    when != v4l2_async_notifier_add_fwnode_subdev(<...x...>)
> > >
> > > Would the specification variant “<+... x ...+>” be relevant
> > > for the parameter selection?
> >
> > I'm indeed quite surprised that <...x...> would be accepted by the parser..
>
> Hi julia,
>
> Thank you for your comments.
> We tested and found that both <...x...> and <+... x ...+> variants work fine.
> We use <... x ...> instead of <+... x ...+> here to eliminate the following false positives:
>
> ./drivers/media/platform/qcom/camss/camss.c:504:1-7: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 479, but without a corresponding object release within this function.
>
> 465 static int camss_of_parse_ports(struct camss *camss)
> 466 {
> ...
> 479 remote = of_graph_get_remote_port_parent(node);
> ...
> 486 asd = v4l2_async_notifier_add_fwnode_subdev(
> 487 &camss->notifier, of_fwnode_handle(remote), ---> v4l2_async_notifier_add_fwnode_subdev will pass remote to camss->notifier.
> 488 sizeof(*csd));
> ...
> 504 return num_subdevs;

I suspect that what is happening is that there is a runtime error, but
that error is caught somewhere and you don't see it.  Could you send me
again the entire semantic patch so I can check on this?

I think that what you want is:

when != v4l2_async_notifier_add_fwnode_subdev(...,<+...x...+>,...)

ie x occurring somewhere within some argument.

julia