linux-kernel - Re: [PATCH 11/12] sched: use for_each

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Message-ID: <CAKMK7uEr9PJ0mex5CWdws55OwaLuHCbLJ5vP8KA4ZQXdAVOTYQ@mail.gmail.com>
Date:   Mon, 9 Jul 2018 17:00:07 +0200
From:   Daniel Vetter <daniel.vetter@...ll.ch>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 11/12] sched: use for_each_if in topology.h

On Mon, Jul 9, 2018 at 12:36 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Mon, Jul 09, 2018 at 10:36:49AM +0200, Daniel Vetter wrote:
>> Avoids complaints from gcc about ambiguous else clauses.
>
> Is that a new thing? I'm fairly sure I've never seen it do that,
>
>> Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>> Cc: Peter Zijlstra <peterz@...radead.org>
>> ---
>>  include/linux/topology.h | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/include/linux/topology.h b/include/linux/topology.h
>> index cb0775e1ee4b..4fba5a5b148d 100644
>> --- a/include/linux/topology.h
>> +++ b/include/linux/topology.h
>> @@ -40,7 +40,7 @@
>>
>>  #define for_each_node_with_cpus(node)                        \
>>       for_each_online_node(node)                      \
>> -             if (nr_cpus_node(node))
>> +             for_each_if (nr_cpus_node(node))
>
> Not having gotten any of the other patches, I'm not really sure what
> this does and such, but improve readability it does not :/

Patch 1 in this series, which I dumped onto lkml as a whole:

https://lkml.org/lkml/2018/7/9/179

Imo it does improve readability for the if (!cond) {} else pattern.
And (assuming my grep fu isn't too badly wrong) most places in the
kernel do use this pattern in for_each macros, so I guess its a real
thing. We've definitely hit it plenty in drm iterators (but we seem to
like if() checks in iterator macros maybe a bit too much).

I'm happy to drop this patch tough if you deem it offensive.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch