Revert "Prevent starvation when acquiring mutex over and over (#15877)" (#15990)

This reverts commit 994257ab06072df38de024e70a60aa9a87e36089.

I saw some failures in CI that are probably related to the change.
Example:

```
 1) Failure:
  TestMonitor#test_timedwait [/Users/runner/work/ruby/ruby/src/test/monitor/test_monitor.rb:282]:
```

This starvation problem has not been an issue in real apps afaik, so for now it's best to revert
it and think of a better solution.

1 files changed, 0 insertions, 35 deletions

diff --git a/test/ruby/test_thread.rb b/test/ruby/test_thread.rb
index 47a8e94c07..b2d8e73693 100644
--- a/test/ruby/test_thread.rb
+++ b/test/ruby/test_thread.rb
@@ -1664,39 +1664,4 @@ q.pop
       assert_operator elapsed, :>=, 0.1, "sub-millisecond sleeps should not return immediately"
     end;
   end
-
-  # [Bug #21840]
-  def test_mutex_owner_doesnt_starve_waiters
-    assert_separately([], "#{<<~"begin;"}\n#{<<~'end;'}")
-    begin;
-      require "tempfile"
-      temp = Tempfile.new("temp")
-      m = Mutex.new
-
-      def fib(n)
-        return n if n <= 1
-        fib(n - 1) + fib(n - 2)
-      end
-
-      t1_running = false
-      Thread.new do
-        t1_running = true
-        loop do
-          fib(20)
-          m.synchronize do
-            File.open(temp.path) { } # reset timeslice due to blocking operation
-          end
-        end
-      end
-
-      loop until t1_running
-
-      3.times.map do
-        Thread.new do
-          m.synchronize do
-          end
-        end
-      end.each(&:join)
-    end;
-  end
 end