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

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Date:	Fri, 17 Jun 2016 17:28:47 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Namhyung Kim <namhyung@...nel.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

On Tue, 24 May 2016 12:02:35 +0900
Namhyung Kim <namhyung@...nel.org> wrote:

> On Mon, May 23, 2016 at 10:32:43PM -0400, Steven Rostedt wrote:
> > On Tue, 24 May 2016 11:16:31 +0900
> > Namhyung Kim <namhyung@...nel.org> wrote:
> > 
> >   
> > > Why not checking "hist" file then?  
> > 
> > I guess that could be done too, but is there anything wrong with my
> > current solution? Or is it just too hacky? How would one check if
> > something exists in a file or not? Say, I want to detect if
> > preemptirqsoff tracer exists or not, and that only happens if I do a
> > grep of current_tracer (I have tests coming that will need to do that)?  
> 
> There's nothing wrong with your approach IMHO.  But I think checking
> existence of a file is clearer and consistent to other tests.
> 
> For the preemptirqsoff tracer case, it seems there's no other way to
> check it simply.  It's not hacky to me grep-ing contents to check
> availability of some option.
> 

Ah, due to traveling I never got around to finishing this. What about
this patch?

>From 7bf19b58ba02e66014efce6c051acba2c6cbd861 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>
Date: Mon, 23 May 2016 15:06:30 -0400
Subject: [PATCH] ftracetest: Fix hist unsupported result in hist selftests

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.

Namhyung Kim recommended to test for the "hist" file located in
events/sched/sched_process_fork/hist instead, as it is more inline with the
other checks. As the hist file is only created if the histogram feature is
enabled, that is a valid check.

Link: http://lkml.kernel.org/r/20160523151538.4ea9ce0c@gandalf.local.home

Suggested-by: Namhyung Kim <namhyung@...nel.org>
Fixes: 76929ab51f0ee ("kselftests/ftrace: Add hist trigger testcases")
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
---
 .../testing/selftests/ftrace/test.d/trigger/trigger-hist-mod.tc  | 9 ++++-----
 tools/testing/selftests/ftrace/test.d/trigger/trigger-hist.tc    | 9 ++++-----
 .../testing/selftests/ftrace/test.d/trigger/trigger-multihist.tc | 9 ++++-----
 3 files changed, 12 insertions(+), 15 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..0bf5085281f3 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
@@ -23,15 +23,14 @@ if [ ! -f events/sched/sched_process_fork/trigger ]; then
     exit_unsupported
 fi
 
-reset_tracer
-do_reset
-
-FEATURE=`grep hist events/sched/sched_process_fork/trigger`
-if [ -z "$FEATURE" ]; then
+if [ ! -f events/sched/sched_process_fork/hist ]; then
     echo "hist trigger is not supported"
     exit_unsupported
 fi
 
+reset_tracer
+do_reset
+
 echo "Test histogram with execname modifier"
 
 echo 'hist:keys=common_pid.execname' > events/sched/sched_process_fork/trigger
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..a00184cd9c95 100644
--- a/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist.tc
+++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist.tc
@@ -23,15 +23,14 @@ if [ ! -f events/sched/sched_process_fork/trigger ]; then
     exit_unsupported
 fi
 
-reset_tracer
-do_reset
-
-FEATURE=`grep hist events/sched/sched_process_fork/trigger`
-if [ -z "$FEATURE" ]; then
+if [ ! -f events/sched/sched_process_fork/hist ]; then
     echo "hist trigger is not supported"
     exit_unsupported
 fi
 
+reset_tracer
+do_reset
+
 echo "Test histogram basic tigger"
 
 echo 'hist:keys=parent_pid:vals=child_pid' > events/sched/sched_process_fork/trigger
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..3478b00ead57 100644
--- a/tools/testing/selftests/ftrace/test.d/trigger/trigger-multihist.tc
+++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-multihist.tc
@@ -23,15 +23,14 @@ if [ ! -f events/sched/sched_process_fork/trigger ]; then
     exit_unsupported
 fi
 
-reset_tracer
-do_reset
-
-FEATURE=`grep hist events/sched/sched_process_fork/trigger`
-if [ -z "$FEATURE" ]; then
+if [ ! -f events/sched/sched_process_fork/hist ]; then
     echo "hist trigger is not supported"
     exit_unsupported
 fi
 
+reset_tracer
+do_reset
+
 reset_trigger
 
 echo "Test histogram multiple tiggers"
-- 
1.9.3