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Date: Tue, 31 Mar 2015 02:08:06 +0100 From: Pádraig Brady <P@...igBrady.com> To: Namhyung Kim <namhyung@...nel.org>, Steven Rostedt <rostedt@...dmis.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 31/03/15 01:48, Namhyung Kim wrote: > Hi Steve, > > On Mon, Mar 30, 2015 at 05:15:11PM -0400, Steven Rostedt wrote: >> 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. > > I understand your point. But this is not just cat, it needs grep and > wc also. So I think there should be scheduler event(s). > >> >> What about using: >> >> ping localhost -c 1 >> >> ? > > I'm okay with ping though but worried if some tiny system might lack > the ping command.. I'd use a fallback method like: yield() { sleep .001 || usleep 1 || sleep 1; } Then just s/usleep 1/yield/ cheers, Pádraig. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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