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Subject: Re: [PATCH 2/2] hw-breakpoints: Add two reserved fields for future
 extensions
From: Peter Zijlstra <peterz@infradead.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>,
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Date: Thu, 03 Dec 2009 22:33:39 +0100
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On Thu, 2009-12-03 at 22:16 +0100, Frederic Weisbecker wrote:

> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index 771d04c..89832cc 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -221,6 +221,8 @@ struct perf_event_attr {
>  			__u64		bp_end;
>  			__u32		bp_type;
>  			__u32		bp_len;
> +			__u64		__bp_reserved_1;
> +			__u64		__bp_reserved_2;
>  		};
>  	};

Looking at that code I see:

 union {
  struct {
  }
 }

wth is that union for?