linux-kernel - Re: [PATCH v5 5/9] perf auxtrace: Use WRITE_ONCE() for updating aux

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Date:   Mon, 9 Aug 2021 16:59:51 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Leo Yan <leo.yan@...aro.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Michael Petlan <mpetlan@...hat.com>,
        "Frank Ch. Eigler" <fche@...hat.com>,
        Song Liu <songliubraving@...com>, x86@...nel.org,
        Daniel Díaz <daniel.diaz@...aro.org>,
        Andrii Nakryiko <andriin@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        coresight@...ts.linaro.org
Subject: Re: [PATCH v5 5/9] perf auxtrace: Use WRITE_ONCE() for updating
 aux_tail

Em Mon, Aug 09, 2021 at 07:14:03PM +0800, Leo Yan escreveu:
> Use WRITE_ONCE() for updating aux_tail, so can avoid unexpected memory
> behaviour.

Thanks, applied to perf/core.

- Arnaldo

 
> Signed-off-by: Leo Yan <leo.yan@...aro.org>
> Acked-by: Adrian Hunter <adrian.hunter@...el.com>
> Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  tools/perf/util/auxtrace.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/auxtrace.h b/tools/perf/util/auxtrace.h
> index cc1c1b9cec9c..79227b8864cd 100644
> --- a/tools/perf/util/auxtrace.h
> +++ b/tools/perf/util/auxtrace.h
> @@ -480,7 +480,7 @@ static inline void auxtrace_mmap__write_tail(struct auxtrace_mmap *mm, u64 tail)
>  	/* Ensure all reads are done before we write the tail out */
>  	smp_mb();
>  #if BITS_PER_LONG == 64 || !defined(HAVE_SYNC_COMPARE_AND_SWAP_SUPPORT)
> -	pc->aux_tail = tail;
> +	WRITE_ONCE(pc->aux_tail, tail);
>  #else
>  	do {
>  		old_tail = __sync_val_compare_and_swap(&pc->aux_tail, 0, 0);
> -- 
> 2.25.1
> 

-- 

- Arnaldo