linux-kernel - Re: [GIT PULL 0/7] perf/core improvements and fixes

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Date:	Thu, 26 Nov 2015 12:00:00 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	linux-kernel@...r.kernel.org, David Ahern <dsahern@...il.com>,
	Jan Kratochvil <jkratoch@...hat.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Milian Wolff <milian.wolff@...b.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Taeung Song <treeze.taeung@...il.com>,
	Wang Nan <wangnan0@...wei.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [GIT PULL 0/7] perf/core improvements and fixes


* Jiri Olsa <jolsa@...hat.com> wrote:

> I think I found one race..
>  - having install-traceevent-plugins depend on $(LIBTRACEEVENT),
>    plugins will not be built as its prereq. and the target
>    install-traceevent-plugins itself will trigger plugins build
>  - but plugins build is also triggered by perf build itself
>    via libtraceevent_plugins target
> 
> so those 2 might race.. but as I said, I've never reproduced ;-)
> 
> Could you please give it a try?
> 
> thanks,
> jirka
> 
> 
> ---
> diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> index 0d19d5447d6c..929a32ba15f5 100644
> --- a/tools/perf/Makefile.perf
> +++ b/tools/perf/Makefile.perf
> @@ -420,7 +420,7 @@ $(LIBTRACEEVENT)-clean:
>  	$(call QUIET_CLEAN, libtraceevent)
>  	$(Q)$(MAKE) -C $(TRACE_EVENT_DIR) O=$(OUTPUT) clean >/dev/null
>  
> -install-traceevent-plugins: $(LIBTRACEEVENT)
> +install-traceevent-plugins: libtraceevent_plugins
>  	$(Q)$(MAKE) -C $(TRACE_EVENT_DIR) $(LIBTRACEEVENT_FLAGS) O=$(OUTPUT) install_plugins
>  

Ok, so I tried this fix with my 'sleep 1' hack to make the race easier to trigger, 
and without your fix it still fails fairly quickly:

triton:~/tip/tools/perf> while : ; do echo -n "$(date) "; make clean install V=1 >/tmp/FAIL.log 2>&1 && echo pass || { echo 'FAIL!'; break; } done
Thu Nov 26 11:54:36 CET 2015 pass
Thu Nov 26 11:54:47 CET 2015 FAIL!

but with your fix applied it passes a reasonable number of builds:

triton:~/tip/tools/perf> while : ; do echo -n "$(date) "; make clean install V=1 >/tmp/FAIL.log 2>&1 && echo pass || { echo 'FAIL!'; break; } done
Thu Nov 26 11:55:12 CET 2015 pass
Thu Nov 26 11:55:25 CET 2015 pass
Thu Nov 26 11:55:36 CET 2015 pass
Thu Nov 26 11:55:47 CET 2015 pass
Thu Nov 26 11:55:58 CET 2015 pass
Thu Nov 26 11:56:09 CET 2015 pass
Thu Nov 26 11:56:21 CET 2015 pass
Thu Nov 26 11:56:32 CET 2015 pass
Thu Nov 26 11:56:44 CET 2015 pass
Thu Nov 26 11:56:55 CET 2015 pass
Thu Nov 26 11:57:06 CET 2015 pass
Thu Nov 26 11:57:18 CET 2015 pass
Thu Nov 26 11:57:29 CET 2015 pass
Thu Nov 26 11:57:40 CET 2015 pass
Thu Nov 26 11:57:51 CET 2015 pass
Thu Nov 26 11:58:03 CET 2015 pass

So I think the bug is fixed for good:

  Tested-by: Ingo Molnar <mingo@...nel.org>

( I'll keep it running some longer and will let you know if there's any failure.
  Consider it fixed if I don't send any update. )

Thanks,

	Ingo
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