linux-kernel - Re: [PATCH] llist: Put parentheses around parameters of llist_for_each_entry

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Message-ID: <8760c6c59e.fsf@yhuang-dev.intel.com>
Date:   Tue, 26 Sep 2017 15:01:49 +0800
From:   "Huang\, Ying" <ying.huang@...el.com>
To:     Byungchul Park <byungchul.park@....com>
Cc:     <peterz@...radead.org>, <mingo@...nel.org>,
        <linux-kernel@...r.kernel.org>, <kernel-team@....com>,
        <ying.huang@...el.com>
Subject: Re: [PATCH] llist: Put parentheses around parameters of llist_for_each_entry_safe()

Hi, Byungchul,

Byungchul Park <byungchul.park@....com> writes:

> It would be somewhat safer to put parentheses around parameters of
> a macro with parameters. Put it.
>
> Signed-off-by: Byungchul Park <byungchul.park@....com>
> ---
>  include/linux/llist.h | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/llist.h b/include/linux/llist.h
> index 1957635..e280b297 100644
> --- a/include/linux/llist.h
> +++ b/include/linux/llist.h
> @@ -183,10 +183,10 @@ static inline void init_llist_head(struct llist_head *list)
>   * reverse the order by yourself before traversing.
>   */
>  #define llist_for_each_entry_safe(pos, n, node, member)			       \
> -	for (pos = llist_entry((node), typeof(*pos), member);		       \
> +	for ((pos) = llist_entry((node), typeof(*(pos)), member);		       \
>  	     member_address_is_nonnull(pos, member) &&			       \
> -	        (n = llist_entry(pos->member.next, typeof(*n), member), true); \
> -	     pos = n)
> +	        ((n) = llist_entry((pos)->member.next, typeof(*(n)), member), true); \
> +	     (pos) = (n))
>  
>  /**
>   * llist_empty - tests whether a lock-less list is empty

The original code follows the style of list_for_each_entry_safe().  The
parameters "pos" and "n" must be variable.  Because list_xxx family
functions work well so far, I think we needn't to change it too.

Best Regards,
Huang, Ying