linux-kernel - Re: [PATCH] perf tools: session: avoid infinite loop

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Date:	Fri, 18 Sep 2015 14:37:09 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Adrian Hunter <adrian.hunter@...el.com>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>, Jiri Olsa <jolsa@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] perf tools: session: avoid infinite loop

> > So it looks like I shouldn't have any synthesized events. Have I missed
> > anything?
> 
> Yes, you are right.  But you are not getting the COMM and MMAP events from
> the exec which means you are killing perf before it execs the workload.

Oh, I see.

> Perf writes through a pipe to its forked child to do the exec, so
> to reproduce it you just need to put everything on the same cpu and play around
> with the sleep number
> 
> 	taskset -c 0 tools/perf/perf record -- sleep 1 & sleep 0.005 ; kill -2 $!
> 
> reproduces the problem for me.  Of course, since the workload doesn't get exec'ed
> it doesn't matter if it is bogus i.e.
> 
> 	taskset -c 0 tools/perf/perf record -- sdfgsdgdg & sleep 0.005 ; kill -2 $!
> 
> also reproduces the problem.

Thanks for confirming!

Mark.
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