add new boot.InUse() helper and use in the garbage collector

boot/kernel_os.go

@@ -176,3 +176,28 @@ func KernelOrOsRebootRequired(s *snap.Info) bool {
 
 	return false
 }
+
+// InUse checks if the given name/revision is used in the
+// boot environment
+func InUse(name string, rev snap.Revision) bool {
+	bootloader, err := partition.FindBootloader()
+	if err != nil {
+		logger.Noticef("cannot get boot settings: %s", err)
+		return false
+	}
+
+	m, err := bootloader.GetBootVars("snap_kernel", "snap_try_kernel", "snap_core", "snap_try_core")
+	if err != nil {
+		logger.Noticef("cannot get boot vars: %s", err)
+		return false
+	}
+
+	for _, v := range m {
+		// FIXME: fugly code/behavior duplication
+		if v == fmt.Sprintf("%s_%s.snap", name, rev) {
+			return true
+		}
+	}
+
+	return false
+}

overlord/snapstate/snapstate.go

@@ -26,6 +26,7 @@ import (
 	"reflect"
 	"sort"
 
+	"github.com/snapcore/snapd/boot"
 	"github.com/snapcore/snapd/i18n"
 	"github.com/snapcore/snapd/logger"
 	"github.com/snapcore/snapd/overlord/auth"
@@ -149,6 +150,9 @@ func doInstall(s *state.State, snapst *SnapState, ss *SnapSetup) (*state.TaskSet
 		// normal garbage collect
 		for i := 0; i <= currentIndex-2; i++ {
 			si := seq[i]
+			if boot.InUse(ss.Name(), si.Revision) {
+				continue
+			}
 			ts := removeInactiveRevision(s, ss.Name(), si.Revision)
 			ts.WaitFor(prev)
 			tasks = append(tasks, ts.Tasks()...)