Subject: Re: [PATCH v2 7/8] perf auxtrace: Use WRITE_ONCE() for updating aux_tail

From: Arnaldo Carvalho de Melo <[email-masked]>
Date: Tue, 8 Jun 2021 14:04:30 -0300

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 <[email-masked]>
> 
> Acked-by: Peter Zijlstra (Intel) <[email-masked]>

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

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