vm/qemu: detect boot errors faster

Currently we try to ssh into the machine for 10 minutes
even if it crashed right away. Make qemu exit on kernel panic
and stop ssh'ing when qemu exits.
Handling bad kernels fast is actually important for bisection.

Update #501

1 files changed, 6 insertions, 2 deletions

diff --git a/vm/vmimpl/util.go b/vm/vmimpl/util.go
index c7462c2cf..418ae2d66 100644
--- a/vm/vmimpl/util.go
+++ b/vm/vmimpl/util.go
@@ -22,7 +22,7 @@ func SleepInterruptible(d time.Duration) bool {
 	}
 }
 
-func WaitForSSH(debug bool, timeout time.Duration, addr, sshKey, sshUser, OS string, port int) error {
+func WaitForSSH(debug bool, timeout time.Duration, addr, sshKey, sshUser, OS string, port int, stop chan error) error {
 	pwd := "pwd"
 	if OS == "windows" {
 		pwd = "dir"
@@ -30,7 +30,11 @@ func WaitForSSH(debug bool, timeout time.Duration, addr, sshKey, sshUser, OS str
 	startTime := time.Now()
 	SleepInterruptible(5 * time.Second)
 	for {
-		if !SleepInterruptible(5 * time.Second) {
+		select {
+		case <-time.After(5 * time.Second):
+		case err := <-stop:
+			return err
+		case <-Shutdown:
 			return fmt.Errorf("shutdown in progress")
 		}
 		args := append(SSHArgs(debug, sshKey, port), sshUser+"@"+addr, pwd)