linux-kernel - Re: [PATCH v2 7/8] perf auxtrace: Use WRITE_ONCE() for updating aux

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Date:   Tue, 8 Jun 2021 14:04:30 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Leo Yan <leo.yan@...aro.org>, 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>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 7/8] perf auxtrace: Use WRITE_ONCE() for updating
 aux_tail

Em Mon, Jun 07, 2021 at 05:31:01PM +0200, Peter Zijlstra escreveu:
> On Wed, Jun 02, 2021 at 06:30:06PM +0800, Leo Yan wrote:
> > Use WRITE_ONCE() for updating aux_tail, so can avoid unexpected memory
> > behaviour.
> > 
> > Signed-off-by: Leo Yan <leo.yan@...aro.org>
> 
> Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>

Leo, this one is dependendant on the 6/8, will wait for a resubmission,
keeping 5/8 tho, as was Acked and applies cleanly, perf/core.
 
> > ---
> >  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 e625bc76cdde..abc4282f5272 100644
> > --- a/tools/perf/util/auxtrace.h
> > +++ b/tools/perf/util/auxtrace.h
> > @@ -458,7 +458,7 @@ 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();
> > -	pc->aux_tail = tail;
> > +	WRITE_ONCE(pc->aux_tail, tail);
> >  }
> >  
> >  int auxtrace_mmap__mmap(struct auxtrace_mmap *mm,
> > -- 
> > 2.25.1
> > 

-- 

- Arnaldo