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Subject[PATCH 1/2] ftrace/selftests: workaround cgroup RT scheduling issues
Date
wakeup_rt.tc and wakeup.tc tests in tracers/ subdirectory
fail due to the chrt command returning:

chrt: failed to set pid 0's policy: Operation not permitted.

To work around this, temporarily disable grout RT scheduling
during ftracetest execution. Restore original value on
test run completion. With these changes in place, both
tests consistently pass.

Fixes: c575dea2c1a5 ("selftests/ftrace: Add wakeup_rt tracer testcase")
Fixes: c1edd060b413 ("selftests/ftrace: Add wakeup tracer testcase")
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
---
tools/testing/selftests/ftrace/ftracetest | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)

diff --git a/tools/testing/selftests/ftrace/ftracetest b/tools/testing/selftests/ftrace/ftracetest
index 063ecb2..3207bbf 100755
--- a/tools/testing/selftests/ftrace/ftracetest
+++ b/tools/testing/selftests/ftrace/ftracetest
@@ -29,8 +29,26 @@ err_ret=1
# kselftest skip code is 4
err_skip=4

+# cgroup RT scheduling prevents chrt commands from succeeding, which
+# induces failures in test wakeup tests. Disable for the duration of
+# the tests.
+sched_rt_runtime=$(sysctl -n kernel.sched_rt_runtime_us)
+
+set_sysctl() {
+ sysctl -qw ${1}=${2} >/dev/null 2>&1
+}
+
+setup() {
+ set_sysctl kernel.sched_rt_runtime_us -1
+}
+
+cleanup() {
+ set_sysctl kernel.sched_rt_runtime_us $sched_rt_runtime
+}
+
errexit() { # message
echo "Error: $1" 1>&2
+ cleanup
exit $err_ret
}

@@ -39,6 +57,8 @@ if [ `id -u` -ne 0 ]; then
errexit "this must be run by root user"
fi

+setup
+
# Utilities
absdir() { # file_path
(cd `dirname $1`; pwd)
@@ -235,6 +255,7 @@ TOTAL_RESULT=0

INSTANCE=
CASENO=0
+
testcase() { # testfile
CASENO=$((CASENO+1))
desc=`grep "^#[ \t]*description:" $1 | cut -f2 -d:`
@@ -406,5 +427,7 @@ prlog "# of unsupported: " `echo $UNSUPPORTED_CASES | wc -w`
prlog "# of xfailed: " `echo $XFAILED_CASES | wc -w`
prlog "# of undefined(test bug): " `echo $UNDEFINED_CASES | wc -w`

+cleanup
+
# if no error, return 0
exit $TOTAL_RESULT
--
1.8.3.1
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