create a lock file during builds

prevent duplicate main instances of the build
system from running

the lock file is deleted when the parent process
exits, alongside the tmpdir deletion

the build system must only ever be run ot one
instance at a time, per work directory

Signed-off-by: Leah Rowe <leah@libreboot.org>

3 files changed, 13 insertions, 9 deletions

diff --git a/.gitignore b/.gitignore
index 25c27d4c..d6c27f5d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -30,3 +30,4 @@
 /src/
 /CHANGELOG
 /todo.txt
+/lock
diff --git a/build b/build
index 74ea1de6..bfd865c2 100755
--- a/build
+++ b/build
@@ -124,7 +124,8 @@ fetch_trees()
 
 fail()
 {
-	tmp_cleanup || printf "WARNING: can't rm tmpdir: %s\n" "$tmpdir" 1>&2
+	tmp_cleanup || printf "WARNING: can't rm tmp files: %s\n" "$tmpdir" \
+	    1>&2
 	err_ "${1}"
 }
 
@@ -132,6 +133,7 @@ tmp_cleanup()
 {
 	[ "$tmpdir_was_set" = "n" ] || return 0
 	rm -Rf "$tmpdir" || return 1
+	rm -f lock || return 1
 }
 
 main $@
diff --git a/include/lib.sh b/include/lib.sh
index b3a76879..b41645fb 100755
--- a/include/lib.sh
+++ b/include/lib.sh
@@ -65,27 +65,28 @@ install_packages()
 id -u 1>/dev/null 2>/dev/null || $err "suid check failed (id -u)"
 [ "$(id -u)" != "0" ] || $err "this command as root is not permitted"
 
-# if "y": a coreboot target won't be built if target.cfg says release="n"
-# (this is used to exclude certain build targets from releases)
-
-[ -z "${XBMK_RELEASE+x}" ] && xbmk_release="n"
-[ -z "$xbmk_release" ] && xbmk_release="$XBMK_RELEASE"
-[ "$xbmk_release" = "n" ] || [ "$xbmk_release" = "y" ] || xbmk_release="n"
-export XBMK_RELEASE="$xbmk_release"
-
 [ -z "${TMPDIR+x}" ] && tmpdir_was_set="n"
 if [ "$tmpdir_was_set" = "y" ]; then
 	[ "${TMPDIR%_*}" = "/tmp/xbmk" ] || tmpdir_was_set="n"
 fi
 if [ "$tmpdir_was_set" = "n" ]; then
+	[ -f "lock" ] && $err "The 'lock' file exists. Is a build running?"
 	export TMPDIR="/tmp"
 	tmpdir="$(mktemp -d -t xbmk_XXXXXXXX)"
 	export TMPDIR="$tmpdir"
+	touch lock || $err "cannot create 'lock' file"
 else
 	export TMPDIR="$TMPDIR"
 	tmpdir="$TMPDIR"
 fi
 
+# if "y": a coreboot target won't be built if target.cfg says release="n"
+# (this is used to exclude certain build targets from releases)
+[ -z "${XBMK_RELEASE+x}" ] && xbmk_release="n"
+[ -z "$xbmk_release" ] && xbmk_release="$XBMK_RELEASE"
+[ "$xbmk_release" = "n" ] || [ "$xbmk_release" = "y" ] || xbmk_release="n"
+export XBMK_RELEASE="$xbmk_release"
+
 [ -z "${XBMK_THREADS+x}" ] || threads="$XBMK_THREADS"
 [ -z "$threads" ] && threads=1
 expr "X$threads" : "X-\{0,1\}[0123456789][0123456789]*$" \