utils: Make WaitLocalProcess safer

Rather than relying on the system clock, use a channel timeout to avoid
problems if the system time changed.

Signed-off-by: James O. D. Hunt <james.o.hunt@intel.com>

src/runtime/virtcontainers/utils/utils.go

@@ -345,10 +345,16 @@ func WaitLocalProcess(pid int, timeoutSecs uint, initialSignal syscall.Signal, l
 
 	pidRunning := true
 
-	// Wait for the VM process to terminate
+	secs := time.Duration(timeoutSecs)
-	startTime := time.Now()
+	timeout := time.After(secs * time.Second)
 
+	// Wait for the VM process to terminate
+outer:
 	for {
+		select {
+		case <-time.After(50 * time.Millisecond):
+			// Check if the process is running periodically to avoid a busy loop
+
 			var _status syscall.WaitStatus
 			var _rusage syscall.Rusage
 			var waitedPid int
@@ -358,24 +364,21 @@ func WaitLocalProcess(pid int, timeoutSecs uint, initialSignal syscall.Signal, l
 
 			if waitedPid == pid && err == nil {
 				pidRunning = false
-			break
+				break outer
 			}
 
 			if err = syscall.Kill(pid, syscall.Signal(0)); err != nil {
 				pidRunning = false
-			break
+				break outer
 			}
 
-		if time.Since(startTime).Seconds() >= float64(timeoutSecs) {
+			break
-			pidRunning = true
 
+		case <-timeout:
 			logger.Warnf("process %v still running after waiting %ds", pid, timeoutSecs)
 
-			break
+			break outer
 		}
-
-		// Brief pause to avoid a busy loop
-		time.Sleep(time.Duration(50) * time.Millisecond)
 	}
 
 	if pidRunning {