[PATCH 5/7] selftests: ftrace: Fix trigger extended error testcase

From: Steven Rostedt
Date: Thu Apr 26 2018 - 13:32:44 EST

From: Masami Hiramatsu <mhiramat@xxxxxxxxxx>

Previous testcase redirects echo-out into /dev/null
using "&>" as below

echo "trigger-command" >> trigger &> /dev/null

But this means redirecting both stdout and stderr into
/dev/null because it is same as below

echo "trigger-command" >> trigger > /dev/null 2>&1

So ">> trigger" redirects stdout to trigger file, but
next "> /dev/null" redirects stdout to /dev/null again
and the last "2>/&1" redirects stderr to stdout (/dev/null)

This fixes it by "2> /dev/null". And also, since it
must fail, add "!" to echo command.

Link: http://lkml.kernel.org/r/152292052250.15769.12565292689264162435.stgit@devbox

Fixes: f06eec4d0f2c ("selftests: ftrace: Add inter-event hist triggers testcases")
Reviewed-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
Tested-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
.../ftrace/test.d/trigger/inter-event/trigger-extended-error-support.tc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/ftrace/test.d/trigger/inter-event/trigger-extended-error-support.tc b/tools/testing/selftests/ftrace/test.d/trigger/inter-event/trigger-extended-error-support.tc
index 786dce7e48be..2aabab363cfb 100644
--- a/tools/testing/selftests/ftrace/test.d/trigger/inter-event/trigger-extended-error-support.tc
+++ b/tools/testing/selftests/ftrace/test.d/trigger/inter-event/trigger-extended-error-support.tc
@@ -29,7 +29,7 @@ do_reset

echo "Test extended error support"
echo 'hist:keys=pid:ts0=common_timestamp.usecs if comm=="ping"' > events/sched/sched_wakeup/trigger
-echo 'hist:keys=pid:ts0=common_timestamp.usecs if comm=="ping"' >> events/sched/sched_wakeup/trigger &>/dev/null
+! echo 'hist:keys=pid:ts0=common_timestamp.usecs if comm=="ping"' >> events/sched/sched_wakeup/trigger 2> /dev/null
if ! grep -q "ERROR:" events/sched/sched_wakeup/hist; then
fail "Failed to generate extended error in histogram"