perf offcpu: Update offcpu test for child process

Record off-cpu data with perf bench sched messaging workload and count
the number of offcpu-time events. Also update the test script not to
run next tests if failed already and revise the error messages.

$ sudo ./perf test offcpu -v
88: perf record offcpu profiling tests :
--- start ---
test child forked, pid 344780
Checking off-cpu privilege
Basic off-cpu test
Basic off-cpu test [Success]
Child task off-cpu test
Child task off-cpu test [Success]
test child finished with 0
---- end ----
perf record offcpu profiling tests: Ok

Signed-off-by: Namhyung Kim <[e-mail]>
Cc: Blake Jones <[e-mail]>
Cc: Hao Luo <[e-mail]>
Cc: Ian Rogers <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Milian Wolff <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Song Liu <[e-mail]>
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/tests/shell/record_offcpu.sh

···
 }
 trap trap_cleanup exit term int
 
-test_offcpu() {
-  echo "Basic off-cpu test"
+test_offcpu_priv() {
+  echo "Checking off-cpu privilege"
+
   if [ `id -u` != 0 ]
   then
-    echo "Basic off-cpu test [Skipped permission]"
+    echo "off-cpu test [Skipped permission]"
     err=2
     return
   fi
-  if perf record --off-cpu -o ${perfdata} --quiet true 2>&1 | grep BUILD_BPF_SKEL
+  if perf record --off-cpu -o /dev/null --quiet true 2>&1 | grep BUILD_BPF_SKEL
   then
-    echo "Basic off-cpu test [Skipped missing BPF support]"
+    echo "off-cpu test [Skipped missing BPF support]"
     err=2
     return
   fi
+}
+
+test_offcpu_basic() {
+  echo "Basic off-cpu test"
+
   if ! perf record --off-cpu -e dummy -o ${perfdata} sleep 1 2> /dev/null
   then
     echo "Basic off-cpu test [Failed record]"
···
   fi
   if ! perf evlist -i ${perfdata} | grep -q "offcpu-time"
   then
-    echo "Basic off-cpu test [Failed record]"
+    echo "Basic off-cpu test [Failed no event]"
     err=1
     return
   fi
···
   echo "Basic off-cpu test [Success]"
 }
 
-test_offcpu
+test_offcpu_child() {
+  echo "Child task off-cpu test"
+
+  # perf bench sched messaging creates 400 processes
+  if ! perf record --off-cpu -e dummy -o ${perfdata} -- \
+    perf bench sched messaging -g 10 > /dev/null 2&>1
+  then
+    echo "Child task off-cpu test [Failed record]"
+    err=1
+    return
+  fi
+  if ! perf evlist -i ${perfdata} | grep -q "offcpu-time"
+  then
+    echo "Child task off-cpu test [Failed no event]"
+    err=1
+    return
+  fi
+  # each process waits for read and write, so it should be more than 800 events
+  if ! perf report -i ${perfdata} -s comm -q -n -t ';' --percent-limit=90 | \
+    awk -F ";" '{ if (NF > 3 && int($3) < 800) exit 1; }'
+  then
+    echo "Child task off-cpu test [Failed invalid output]"
+    err=1
+    return
+  fi
+  echo "Child task off-cpu test [Success]"
+}
+
+
+test_offcpu_priv
+
+if [ $err = 0 ]; then
+  test_offcpu_basic
+fi
+
+if [ $err = 0 ]; then
+  test_offcpu_child
+fi
 
 cleanup
 exit $err