linux-kernel - Re: [PATCH 1/2] Move kfree_call_rcu() to slab

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Date:   Thu, 04 Jan 2018 22:46:13 -0800
From:   Joe Perches <joe@...ches.com>
To:     Matthew Wilcox <willy@...radead.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     Rao Shoaib <rao.shoaib@...cle.com>,
        Boqun Feng <boqun.feng@...il.com>,
        linux-kernel@...r.kernel.org, brouer@...hat.com, linux-mm@...ck.org
Subject: Re: [PATCH 1/2] Move kfree_call_rcu() to slab_common.c

On Thu, 2018-01-04 at 16:07 -0800, Matthew Wilcox wrote:
> On Thu, Jan 04, 2018 at 03:47:32PM -0800, Paul E. McKenney wrote:
> > I was under the impression that typeof did not actually evaluate its
> > argument, but rather only returned its type.  And there are a few macros
> > with this pattern in mainline.
> > 
> > Or am I confused about what typeof does?
> 
> I think checkpatch is confused by the '*' in the typeof argument:
> 
> $ git diff |./scripts/checkpatch.pl --strict
> CHECK: Macro argument reuse 'ptr' - possible side-effects?
> #29: FILE: include/linux/rcupdate.h:896:
> +#define kfree_rcu(ptr, rcu_head)                                        \
> +	__kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head))
> 
> If one removes the '*', the warning goes away.
> 
> I'm no perlista, but Joe, would this regexp modification make sense?
> 
> +++ b/scripts/checkpatch.pl
> @@ -4957,7 +4957,7 @@ sub process {
>                                 next if ($arg =~ /\.\.\./);
>                                 next if ($arg =~ /^type$/i);
>                                 my $tmp_stmt = $define_stmt;
> -                               $tmp_stmt =~ s/\b(typeof|__typeof__|__builtin\w+|typecheck\s*\(\s*$Type\s*,|\#+)\s*\(*\s*$arg\s*\)*\b//g;
> +                               $tmp_stmt =~ s/\b(typeof|__typeof__|__builtin\w+|typecheck\s*\(\s*$Type\s*,|\#+)\s*\(*\**\(*\s*$arg\s*\)*\b//g;

I supposed ideally it'd be more like

$tmp_stmt =~ s/\b(?:typeof|__typeof__|__builtin\w+|typecheck\s*\(\s*$Type\s*,|\#+)\s*\(*(?:\s*\*\s*)*\s*\(*\s*$arg\s*\)*\b//g;

Adding ?: at the start to not capture and
(?:\s*\*\s*)* for any number of * with any
surrounding spacings.