linux-kernel - Re: [PATCH] libperf: fix alignment trap in perf stat

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Date:   Thu, 22 Aug 2019 12:24:35 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Gerald BAEZA <gerald.baeza@...com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-kernel@...r.kernel.org,
        Alexandre TORGUE <alexandre.torgue@...com>,
        Andi Kleen <ak@...ux.intel.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>
Subject: Re: [PATCH] libperf: fix alignment trap in perf stat

Em Thu, Aug 22, 2019 at 09:07:01AM +0000, Gerald BAEZA escreveu:
> Following the patch 'perf stat: Fix --no-scale', an
> alignment trap happens in process_counter_values()
> on ARMv7 platforms due to the attempt to copy non
> 64 bits aligned double words (pointed by 'count')
> via a NEON vectored instruction ('vld1' with 64
> bits alignment constraint).
> 
> This patch sets a 64 bits alignment constraint on
> 'contents[]' field in 'struct xyarray' since the
> 'count' pointer used above points to such a
> structure.

You forgot to add Mathieu and Andi, which I just did.

I think this is ok and I'm applying, please holler anyone if think this
isn't the case,

- Arnaldo
 
> Signed-off-by: Gerald Baeza <gerald.baeza@...com>
> ---
>  tools/perf/lib/include/internal/xyarray.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/lib/include/internal/xyarray.h b/tools/perf/lib/include/internal/xyarray.h
> index 3bf70e4..51e35d6 100644
> --- a/tools/perf/lib/include/internal/xyarray.h
> +++ b/tools/perf/lib/include/internal/xyarray.h
> @@ -2,6 +2,7 @@
>  #ifndef __LIBPERF_INTERNAL_XYARRAY_H
>  #define __LIBPERF_INTERNAL_XYARRAY_H
>  
> +#include <linux/compiler.h>
>  #include <sys/types.h>
>  
>  struct xyarray {
> @@ -10,7 +11,7 @@ struct xyarray {
>  	size_t entries;
>  	size_t max_x;
>  	size_t max_y;
> -	char contents[];
> +	char contents[] __aligned(8);
>  };
>  
>  struct xyarray *xyarray__new(int xlen, int ylen, size_t entry_size);
> -- 
> 2.7.4

-- 

- Arnaldo