update_bootloaders.sh.patch

--- ./chromiumos/src/scripts/update_bootloaders.sh.orig	2017-01-11 23:27:33.257545571 +0900
+++ ./chromiumos/src/scripts/update_bootloaders.sh	2017-07-18 01:02:26.273755130 +0900
@@ -141,6 +141,7 @@
 fi
 
 ESP_FS_DIR=$(mktemp -d /tmp/esp.XXXXXX)
+ESP_LOOP_COPY=$(mktemp /tmp/esp-loop-copy.XXXXXX)
 cleanup() {
   set +e
   if ! safe_umount "${ESP_FS_DIR}"; then
@@ -155,6 +156,7 @@
     sudo losetup -d  "${ESP_DEV}"
   fi
   rm -rf "${ESP_FS_DIR}"
+  rm -f "${ESP_LOOP_COPY}"
 }
 trap cleanup EXIT
 sudo mount "${ESP_DEV}" "${ESP_FS_DIR}"
@@ -193,7 +195,12 @@
   # we cut over from rootfs booting (extlinux).
   if [[ ${FLAGS_install_syslinux} -eq ${FLAGS_TRUE} ]]; then
     safe_umount "${ESP_FS_DIR}"
-    sudo syslinux -d /syslinux "${ESP_DEV}"
+    # We cannot syslinux ESP_DEV directly because of a race condition with udev,
+    # see http://crbug.com/508713
+    sudo dd if="${ESP_DEV}" of="${ESP_LOOP_COPY}" status=none
+    sudo syslinux -d /syslinux "${ESP_LOOP_COPY}"
+    sudo flock --wait 10 -x "${ESP_DEV}" \
+      dd if="${ESP_LOOP_COPY}" of="${ESP_DEV}" status=none
     # mount again for cleanup to free resource gracefully
     sudo mount -o ro "${ESP_DEV}" "${ESP_FS_DIR}"
   fi