cooker.py: Ensure only one copy of bitbake executes at once

The bitbake codebase makes assumptions that only one copy is active
against a given build directory at a given time. This patch adds a
lockfile in TOPDIR to ensure that is the case.

Note that no unlock is needed, that is automatically dropped when
execution terminates.

(Bitbake rev: 6004cbf36c980c2574c1c9153df81a7c55317e17)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/cooker.py

@@ -138,6 +138,13 @@ class BBCooker:
         if not self.configuration.cmd:
             self.configuration.cmd = bb.data.getVar("BB_DEFAULT_TASK", self.configuration.data, True) or "build"
 
+        # Take a lock so only one copy of bitbake can run against a given build
+        # directory at a time
+        lockfile = bb.data.expand("${TOPDIR}/bitbake.lock", self.configuration.data)
+        self.lock = bb.utils.lockfile(lockfile, False, False)
+        if not self.lock:
+            bb.fatal("Only one copy of bitbake should be run against a build directory")
+
         bbpkgs = bb.data.getVar('BBPKGS', self.configuration.data, True)
         if bbpkgs and len(self.configuration.pkgs_to_build) == 0:
             self.configuration.pkgs_to_build.extend(bbpkgs.split())