runqueue: wait and deal with those <defunct> sub-processes as soon as they are os.killed() when "Force stop"

When "Force stop" is performed during the build stage, after os.kill() kills the build sub-processes, there are many <defunct> python processes in the system. In Hob, when the user initiates a new build, os.waitpid() in runqueue_process_waitpid() will be called, and the pids of those <defunct> processes will be returned as result[0], then self.build_pids[result[0]] will throw KeyError exception because now for the new build self.build_pids is empty.

This patch is to address the above issue to collect the results and handle the sub-processes as soon as they are killed.

[Yocto #2186]

(Bitbake rev: e9f4ca467e795bbc520d12b0e7a5985b6ff0a20e)

Signed-off-by: Shane Wang <shane.wang@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/runqueue.py

@@ -1068,6 +1068,7 @@ class RunQueueExecute:
             for k, v in self.build_pids.iteritems():
                 try:
                     os.kill(-k, signal.SIGTERM)
+                    os.waitpid(-1, 0)
                 except:
                     pass
         for pipe in self.build_pipes: