SI-6488: Stop I/O threads prior to Process destruction

src/library/scala/sys/process/ProcessImpl.scala

@@ -222,7 +222,10 @@ private[process] trait ProcessImpl {
       p.exitValue()
     }
     override def destroy() = {
-      try p.destroy()
+      try{
+        outputThreads foreach (_.stop())
+        p.destroy()
+      }
       finally inputThread.interrupt()
     }
   }

test/files/run/t6488.check

@@ -0,0 +1 @@
+Success

test/files/run/t6488.scala

@@ -0,0 +1,11 @@
+import sys.process._
+object Test {
+  // Program that prints "Success" if the command was successfully run then destroyed
+  // It will silently pass if the command "/bin/ls" does not exist
+  // It will fail due to the uncatchable exception in t6488 race condition
+  def main(args: Array[String]) {
+    try Process("/bin/ls").run(ProcessLogger { _ => () }).destroy
+    catch { case _ => () }
+    println("Success")
+  }
+}