From 8ff68249905b367b4b7179aa4c600511bfec5b87 Mon Sep 17 00:00:00 2001
From: Kjell Winblad <kjellwinblad@gmail.com>
Date: Wed, 29 May 2019 10:50:24 +0200
Subject: Fix the test case cpu_sup_SUITE:util_values

The message signaling that the spinning processes had stopped was
previously sent too early.
---
 lib/os_mon/test/cpu_sup_SUITE.erl | 47 ++++++++++++++++++++++++---------------
 1 file changed, 29 insertions(+), 18 deletions(-)

diff --git a/lib/os_mon/test/cpu_sup_SUITE.erl b/lib/os_mon/test/cpu_sup_SUITE.erl
index 3a8346ac44..7a8065c591 100644
--- a/lib/os_mon/test/cpu_sup_SUITE.erl
+++ b/lib/os_mon/test/cpu_sup_SUITE.erl
@@ -155,45 +155,56 @@ tiny_diff(A, B) ->
 
 -define(SPIN_TIME, 1000).
 
+spinner(Parent) ->
+    receive
+        stop -> Parent ! stopped
+    after 0 -> spinner(Parent)
+    end.
+
 %% Test utilization values
 util_values(Config) when is_list(Config) ->
-
+    NrOfProcessors =
+        case erlang:system_info(logical_processors_available) of
+            unknown -> 2;
+            X -> X
+        end,
     Tester = self(),
     Ref = make_ref(),
-    Loop = fun (L) -> L(L) end,
     Spinner = fun () ->
-                      NrOfProcesses = 100,
-                      Loopers = [spawn_link(fun () -> Loop(Loop) end)
-                                 || _ <- lists:seq(1,NrOfProcesses)],
+                      Spinner = self(),
+                      NrOfProcesses = NrOfProcessors,
+                      Loopers =
+                          [spawn_link(fun () -> spinner(Spinner) end)
+                           || _ <- lists:seq(1,NrOfProcesses)],
                       receive after ?SPIN_TIME -> ok end,
-                      [(fun () ->
-                                unlink(Looper),
-                                exit(Looper, kill),
-                                Tester ! Ref
-                       end)()
-                       || Looper <- Loopers]
-
+                      [begin
+                           Looper ! stop,
+                           receive stopped -> ok end
+                       end
+                       || Looper <- Loopers],
+                      Tester ! Ref
               end,
+    Spin = fun () ->
+                   spawn_link(Spinner),
+                   receive Ref -> ok end
+           end,
     cpu_sup:util(),
     receive after ?SPIN_TIME -> ok end,
     LowUtil0 = cpu_sup:util(),
-    NrOfProcessors = erlang:system_info(logical_processors_available),
     case LowUtil0 of
-        U when U > ((100.0 / NrOfProcessors) * 0.5) ->
+        U when U > ((100.0 / NrOfProcessors) * 0.33) ->
             %% We cannot run this test if the system is doing other
             %% work at the same time as the result will be unreliable
             {skip, io_lib:format("CPU utilization was too high (~f%)", [LowUtil0])};
         _ ->
             cpu_sup:util(),
-            spawn_link(Spinner),
-            receive Ref -> ok end,
+            Spin(),
             HighUtil1 = cpu_sup:util(),
 
             receive after ?SPIN_TIME -> ok end,
             LowUtil1 = cpu_sup:util(),
 
-            spawn_link(Spinner),
-            receive Ref -> ok end,
+            Spin(),
             HighUtil2 = cpu_sup:util(),
 
             receive after ?SPIN_TIME -> ok end,
-- 
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