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

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Message-ID: <d7a23585-826c-9042-b8f9-6bd5895cbf16@oracle.com>
Date:   Thu, 4 Jan 2018 18:14:08 -0800
From:   Rao Shoaib <rao.shoaib@...cle.com>
To:     Matthew Wilcox <willy@...radead.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     Joe Perches <joe@...ches.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 01/04/2018 04:07 PM, 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:
Yup.
>
> $ 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;
>                                  $tmp_stmt =~ s/\#+\s*$arg\b//g;
>                                  $tmp_stmt =~ s/\b$arg\s*\#\#//g;
>                                  my $use_cnt = $tmp_stmt =~ s/\b$arg\b//g;
>
Thanks a lot for digging into this. I had to try several variations for 
the warning to go away and don't remember the reason for each change. I 
am not perl literate and the regular expression sacred me ;-).

Shoaib