linux-kernel - Re: [PATCH 0/4] add missing of_node

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Date:	Thu, 22 Oct 2015 15:19:43 +0200 (CEST)
From:	Julia Lawall <julia.lawall@...6.fr>
To:	Rob Herring <robh+dt@...nel.org>
cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	kernel-janitors@...r.kernel.org,
	Frank Rowand <frowand.list@...il.com>,
	Grant Likely <grant.likely@...aro.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/4] add missing of_node_put



On Thu, 22 Oct 2015, Rob Herring wrote:

> +Russell who raised issues with these iterators recently.
>
> On Thu, Oct 22, 2015 at 4:02 AM, Julia Lawall <Julia.Lawall@...6.fr> wrote:
> > The various for_each device_node iterators performs an of_node_get on each
> > iteration, so a break out of the loop requires an of_node_put.
>
> Thanks for this.
>
> Are there any plans to use coccinelle as a checker that developers can
> run to be warned of these problems?

There are three issues I have found so far:

1.  of_node_put before a continue
2.  missing of_node_put before a break
3.  missing of_node get before some more permanent storage of the value

The semantic patches for the first two seem to be working pretty well, so
I could submit them for integration into the kernel.  The third one, I
have only looked at in an ad hoc way so far.

julia

>
> Rob
>
> > The complete semantic patch that fixes this problem is
> > (http://coccinelle.lip6.fr):
> >
> > // <smpl>
> > @r@
> > local idexpression n;
> > expression e1,e2;
> > iterator name for_each_node_by_name, for_each_node_by_type,
> > for_each_compatible_node, for_each_matching_node,
> > for_each_matching_node_and_match, for_each_child_of_node,
> > for_each_available_child_of_node, for_each_node_with_property;
> > iterator i;
> > statement S;
> > expression list [n1] es;
> > @@
> >
> > (
> > (
> > for_each_node_by_name(n,e1) S
> > |
> > for_each_node_by_type(n,e1) S
> > |
> > for_each_compatible_node(n,e1,e2) S
> > |
> > for_each_matching_node(n,e1) S
> > |
> > for_each_matching_node_and_match(n,e1,e2) S
> > |
> > for_each_child_of_node(e1,n) S
> > |
> > for_each_available_child_of_node(e1,n) S
> > |
> > for_each_node_with_property(n,e1) S
> > )
> > &
> > i(es,n,...) S
> > )
> >
> > @@
> > local idexpression r.n;
> > iterator r.i;
> > expression e;
> > expression list [r.n1] es;
> > @@
> >
> >  i(es,n,...) {
> >    ...
> > (
> >    of_node_put(n);
> > |
> >    e = n
> > |
> >    return n;
> > |
> > +  of_node_put(n);
> > ?  return ...;
> > )
> >    ...
> >  }
> >
> > @@
> > local idexpression r.n;
> > iterator r.i;
> > expression e;
> > expression list [r.n1] es;
> > @@
> >
> >  i(es,n,...) {
> >    ...
> > (
> >    of_node_put(n);
> > |
> >    e = n
> > |
> > +  of_node_put(n);
> > ?  break;
> > )
> >    ...
> >  }
> > ... when != n
> >
> > @@
> > local idexpression r.n;
> > iterator r.i;
> > expression e;
> > identifier l;
> > expression list [r.n1] es;
> > @@
> >
> >  i(es,n,...) {
> >    ...
> > (
> >    of_node_put(n);
> > |
> >    e = n
> > |
> > +  of_node_put(n);
> > ?  goto l;
> > )
> >    ...
> >  }
> > ...
> > l: ... when != n// </smpl>
> >
> > ---
> >
> >  drivers/of/irq.c      |    7 +++++--
> >  drivers/of/overlay.c  |    5 ++++-
> >  drivers/of/platform.c |    8 ++++++--
> >  drivers/of/unittest.c |    8 ++++++--
> >  4 files changed, 21 insertions(+), 7 deletions(-)
> --
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