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Date: Tue, 22 Jan 2013 14:40:24 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Mel Gorman <mgorman@suse.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Andrea Arcangeli <aarcange@redhat.com>, Ingo Molnar <mingo@kernel.org>,
        Simon Jeons <simon.jeons@gmail.com>,
        Wanpeng Li <liwanp@linux.vnet.ibm.com>,
        Hugh Dickins <hughd@google.com>, Linux-MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/6] mm: numa: Handle side-effects in
 count_vm_numa_events() for !CONFIG_NUMA_BALANCING
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On Tue, 22 Jan 2013 17:12:39 +0000
Mel Gorman <mgorman@suse.de> wrote:

> The current definitions for count_vm_numa_events() is wrong for
> !CONFIG_NUMA_BALANCING as the following would miss the side-effect.
> 
> 	count_vm_numa_events(NUMA_FOO, bar++);

Stupid macros.

> There are no such users of count_vm_numa_events() but it is a potential
> pitfall. This patch fixes it and converts count_vm_numa_event() so that
> the definitions look similar.

Confused.  The patch doesn't alter count_vm_numa_event().  No matter.

> --- a/include/linux/vmstat.h
> +++ b/include/linux/vmstat.h
> @@ -85,7 +85,7 @@ static inline void vm_events_fold_cpu(int cpu)
>  #define count_vm_numa_events(x, y) count_vm_events(x, y)
>  #else
>  #define count_vm_numa_event(x) do {} while (0)
> -#define count_vm_numa_events(x, y) do {} while (0)
> +#define count_vm_numa_events(x, y) do { (void)(y); } while (0)
>  #endif /* CONFIG_NUMA_BALANCING */
>  
>  #define __count_zone_vm_events(item, zone, delta) \