jruby · Nov 21, 2017 · Nov 21, 2017
Showing with 30 additions and 1 deletion.

+11 −1 core/src/main/java/org/jruby/ext/thread/Mutex.java

+19 −0 spec/ruby/core/mutex/sleep_spec.rb
diff --git a/core/src/main/java/org/jruby/ext/thread/Mutex.java b/core/src/main/java/org/jruby/ext/thread/Mutex.java
@@ -129,15 +129,25 @@ public IRubyObject sleep(ThreadContext context) {
     public IRubyObject sleep(ThreadContext context, IRubyObject timeout) {
         long beg = System.currentTimeMillis();
         double t = timeout.convertToFloat().getDoubleValue();
+
         if (t < 0) throw context.runtime.newArgumentError("negative sleep timeout");
+
         unlock(context);
+
         try {
-            context.getThread().sleep((long) (t * 1000));
+            long millis = (long) (t * 1000);
+
+            if (Double.compare(t, 0.0d) == 0 || millis == 0) {
+                // wait time is zero or smaller than 1ms, so we just proceed
+            } else {
+                context.getThread().sleep(millis);
+            }
         } catch (InterruptedException ex) {
             // ignore interrupted
         } finally {
             lock(context);
         }
+
         return context.runtime.newFixnum((System.currentTimeMillis() - beg) / 1000);
     }
 

diff --git a/spec/ruby/core/mutex/sleep_spec.rb b/spec/ruby/core/mutex/sleep_spec.rb
@@ -71,4 +71,23 @@
     m.lock
     m.sleep(0.01).should be_kind_of(Integer)
   end
+
+  it "wakes up when requesting sleep times near or equal to zero" do
+    times = []
+    val = 1
+
+    # power of two divisor so we eventually get near zero
+    loop do
+      val = val / 16.0
+      times << val
+      break if val == 0.0
+    end
+
+    m = Mutex.new
+    m.lock
+    times.each do |time|
+      # just testing that sleep completes
+      m.sleep(time).should_not == nil
+    end
+  end
 end