try locking alpm db

main.go

@@ -523,11 +523,13 @@ func (b *BuildManager) syncWorker() {
 		}
 
 		// fetch updates between sync runs
+		b.alpmMutex.Lock()
 		check(alpmHandle.Release())
 		setupChroot()
 		var err error
 		alpmHandle, err = initALPM(filepath.Join(conf.Basedir.Chroot, pristineChroot), filepath.Join(conf.Basedir.Chroot, pristineChroot, "/var/lib/pacman"))
 		check(err)
+		b.alpmMutex.Unlock()
 
 		pkgBuilds, err := Glob(filepath.Join(conf.Basedir.Upstream, "/**/PKGBUILD"))
 		check(err)

utils.go

@@ -61,6 +61,7 @@ type BuildManager struct {
 	failedMutex    sync.RWMutex
 	buildProcesses []*os.Process
 	buildProcMutex sync.RWMutex
+	alpmMutex      sync.RWMutex
 }
 
 type Conf struct {
@@ -498,7 +499,9 @@ func isMirrorLatest(h *alpm.Handle, buildPkg *BuildPackage) (bool, alpm.IPackage
 	allDepends = append(allDepends, buildPkg.Srcinfo.MakeDepends...)
 
 	for _, dep := range allDepends {
+		buildManager.alpmMutex.Lock()
 		pkg, err := dbs.FindSatisfier(dep.Value)
+		buildManager.alpmMutex.Unlock()
 		if err != nil {
 			return false, nil, "", UnableToSatisfyError{err}
 		}