bootstraptest/runner: speed up assert_finish by avoiding sleep

We may use IO.select to watch for process exit.  This speeds up
"make test" by 2 seconds for me.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63754 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 8 insertions, 3 deletions

diff --git a/bootstraptest/runner.rb b/bootstraptest/runner.rb
index e807ce5b62..29dfef771a 100755
--- a/bootstraptest/runner.rb
+++ b/bootstraptest/runner.rb
@@ -373,13 +373,18 @@ def assert_finish(timeout_seconds, testsrc, message = '')
     io = IO.popen("#{@ruby} -W0 #{filename}")
     pid = io.pid
     waited = false
-    tlimit = Time.now + timeout_seconds
-    while Time.now < tlimit
+    tlimit = Process.clock_gettime(Process::CLOCK_MONOTONIC) + timeout_seconds
+    diff = timeout_seconds
+    while diff > 0
       if Process.waitpid pid, Process::WNOHANG
         waited = true
         break
       end
-      sleep 0.1
+      if IO.select([io], nil, nil, diff)
+        while String === io.read_nonblock(1024, exception: false)
+        end
+      end
+      diff = tlimit - Process.clock_gettime(Process::CLOCK_MONOTONIC)
     end
     if !waited
       Process.kill(:KILL, pid)