linux-kernel - Re: [RFC][PATCH] ftracetest: Fix hist unsupported result in hist selftests

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Date:	Tue, 24 May 2016 08:54:38 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	LKML <linux-kernel@...r.kernel.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Shuah Khan <shuahkhan@...il.com>,
	<linux-kselftest@...r.kernel.org>
Subject: Re: [RFC][PATCH] ftracetest: Fix hist unsupported result in hist
 selftests

Hi Steve,

On Mon, May 23, 2016 at 03:15:38PM -0400, Steven Rostedt wrote:
> 
> [ Folks, is this a proper work around? ]
> 
> When histograms are not configured in the kernel, the ftracetest histogram
> selftests should return "unsupported" and not "Failed". To detect this, the
> test scripts have:
> 
>  FEATURE=`grep hist events/sched/sched_process_fork/trigger`
>  if [ -z "$FEATURE" ]; then
>      echo "hist trigger is not supported"
>      exit_unsupported
>  fi
> 
> The problem is that '-e' is in effect and any error will cause the program
> to terminate. The grep for 'hist' fails, because it is not compiled it (thus
> unsupported), but because grep has an error code for failing to find the
> string, it causes the program to terminate, and is marked as a failed test.

We have a feature check before doing grep, doesn't it detect such
case?

  if [ ! -f events/sched/sched_process_fork/trigger ]; then
      echo "event trigger is not supported"
      exit_unsupported
  fi


Thanks,
Namhyung


> 
> As a work around, I added "|| echo -n ''" to not let bash terminate the
> script on a failed grep, and then the rest of the script can handle the fact
> that histograms are not supported and return a proper result.
> 
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
> ---
>  tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-mod.tc  | 2 +-
>  tools/testing/selftests/ftrace/test.d/trigger/trigger-hist.tc      | 2 +-
>  tools/testing/selftests/ftrace/test.d/trigger/trigger-multihist.tc | 2 +-
>  3 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-mod.tc b/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-mod.tc
> index c2b61c4fda11..6c100759c758 100644
> --- a/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-mod.tc
> +++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-mod.tc
> @@ -26,7 +26,7 @@ fi
>  reset_tracer
>  do_reset
>  
> -FEATURE=`grep hist events/sched/sched_process_fork/trigger`
> +FEATURE=`grep hist events/sched/sched_process_fork/trigger || echo -n ''`
>  if [ -z "$FEATURE" ]; then
>      echo "hist trigger is not supported"
>      exit_unsupported
> diff --git a/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist.tc b/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist.tc
> index b2902d42a537..8d691dc0c5cc 100644
> --- a/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist.tc
> +++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist.tc
> @@ -26,7 +26,7 @@ fi
>  reset_tracer
>  do_reset
>  
> -FEATURE=`grep hist events/sched/sched_process_fork/trigger`
> +FEATURE=`grep hist events/sched/sched_process_fork/trigger || echo -n ''`
>  if [ -z "$FEATURE" ]; then
>      echo "hist trigger is not supported"
>      exit_unsupported
> diff --git a/tools/testing/selftests/ftrace/test.d/trigger/trigger-multihist.tc b/tools/testing/selftests/ftrace/test.d/trigger/trigger-multihist.tc
> index 03c4a46561fc..1a11e641e97d 100644
> --- a/tools/testing/selftests/ftrace/test.d/trigger/trigger-multihist.tc
> +++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-multihist.tc
> @@ -26,7 +26,7 @@ fi
>  reset_tracer
>  do_reset
>  
> -FEATURE=`grep hist events/sched/sched_process_fork/trigger`
> +FEATURE=`grep hist events/sched/sched_process_fork/trigger || echo -n ''`
>  if [ -z "$FEATURE" ]; then
>      echo "hist trigger is not supported"
>      exit_unsupported
> -- 
> 1.8.3.1
>