linux-kernel - Re: [PATCH] ftracetest: Do not use usleep

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Message-ID: <20150330171511.5722493b@gandalf.local.home>
Date:	Mon, 30 Mar 2015 17:15:11 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Shuah Khan <shuahkh@....samsung.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Dave Jones <davej@...emonkey.org.uk>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: Re: [PATCH] ftracetest: Do not use usleep

On Thu, 26 Mar 2015 09:32:23 +0900
Namhyung Kim <namhyung@...nel.org> wrote:

> The usleep is only provided on distros from Redhat so running ftracetest
> on other distro resulted in failures due to the missing usleep.
> 
> The reason of using [u]sleep in the test was to generate (scheduler)
> events. But as we use 'cat trace | grep | wc -l' to read the events,
> the command themselves already generate some events before reading the
> trace file so no need to call [u]sleep explicitly.

Note, opening "trace" via cat stops tracing. There is a possible race
where the cat will not produce events. My worry is that if the shell
implements its own "cat" command, it may not fork, and open the trace
file. Which would not have any events in it, and opening it will
disable the rest of the command from having events.

What about using:

 ping localhost -c 1

?

-- Steve
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