scripts/pkgbuilder.py: assign each subprocess a process group

When pkgbuilder.py is terminated with SIGINT (ie. ctrl-c), or exits
immediately due to a failed job, it is sometimes possible for child
subprocesses (ie. build tasks) to remain alive and continue running
in the background.

To fix this, assign each subprocess a new process group identifier,
and capture the pid of each child subprocess so that on shutdown we
can kill the entire child process group (ie. kill the child subprocess,
and all subprocesses the child subprocess may have created) for any
builder processes that are still running.

scripts/pkgbuilder.py

@@ -14,6 +14,7 @@ import threading
 import queue
 import subprocess
 import multiprocessing
+import signal
 
 # Ensure we can output any old crap to stdout and stderr
 sys.stdout = codecs.getwriter("utf-8")(sys.stdout.detach())
@@ -33,9 +34,10 @@ class RusagePopen(subprocess.Popen):
             self.rusage = ru
         return (pid, sts)
 
-def rusage_run(*popenargs, timeout=None, **kwargs):
+def rusage_run(*popenargs, parent=None, timeout=None, **kwargs):
     with RusagePopen(*popenargs, **kwargs) as process:
         try:
+            parent.child = process
             stdout, stderr = process.communicate(None, timeout=timeout)
         except subprocess.TimeoutExpired as exc:
             process.kill()
@@ -47,6 +49,7 @@ def rusage_run(*popenargs, timeout=None, **kwargs):
         retcode = process.poll()
     res = subprocess.CompletedProcess(process.args, retcode, stdout, stderr)
     res.rusage = process.rusage
+    parent.child = None
     return res
 
 class GeneratorEmpty(Exception):
@@ -255,11 +258,19 @@ class BuildProcess(threading.Thread):
 
         self.active = False
 
+        self.child = None
+
         self.stopping = False
 
     def stop(self):
         self.stopping = True
         self.work.put(None)
+        if self.child:
+            try:
+                os.killpg(os.getpgid(self.child.pid), signal.SIGTERM)
+                self.child.wait()
+            except:
+                pass
 
     def isActive(self):
         return self.active == True
@@ -305,14 +316,14 @@ class BuildProcess(threading.Thread):
                 with open(job["logfile"], "w") as logfile:
                     cmd = rusage_run(job["args"], cwd=ROOT,
                                      stdin=subprocess.PIPE, stdout=logfile, stderr=subprocess.STDOUT,
-                                     universal_newlines=True, shell=False)
+                                     universal_newlines=True, shell=False, parent=self, start_new_session=True)
                 returncode = cmd.returncode
                 job["cmdproc"] = cmd
             else:
                 try:
                     cmd = rusage_run(job["args"], cwd=ROOT,
                                      stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.STDOUT,
-                                     universal_newlines=True, shell=False,
+                                     universal_newlines=True, shell=False, parent=self, start_new_session=True,
                                      encoding="utf-8", errors="replace")
                     returncode = cmd.returncode
                     job["cmdproc"] = cmd
@@ -434,7 +445,6 @@ class Builder:
             job = None
 
         self.captureStats(finished=True)
-        self.stopProcesses()
 
         if self.joblogfile:
             self.joblogfile.close()
@@ -678,8 +688,13 @@ class Builder:
             process.start()
 
     def stopProcesses(self):
-        for process in self.processes:
-            process.stop()
+        if self.processes:
+            for process in self.processes:
+                process.stop()
+            self.processes = None
+
+    def cleanup(self):
+        self.stopProcesses()
 
     def vprint(self, status, task, data, p1=None, p2=None):
        p1 = (self.threadcount - self.generator.activeJobCount()) if p1 == None else p1
@@ -777,17 +792,22 @@ with open("%s/parallel.pid" % THREAD_CONTROL, "w") as pid:
     print("%d" % os.getpid(), file=pid)
 
 try:
-    result = Builder(args.max_procs, args.plan, args.joblog, args.loadstats, args.stats_interval, \
-                     haltonerror=args.halt_on_error, failimmediately=args.fail_immediately, \
-                     log_burst=args.log_burst, log_combine=args.log_combine, bookends=args.with_bookends, \
-                     autoremove=args.auto_remove, colors=args.colors, \
-                     debug=args.debug, verbose=args.verbose).build()
+    builder = Builder(args.max_procs, args.plan, args.joblog, args.loadstats, args.stats_interval, \
+                      haltonerror=args.halt_on_error, failimmediately=args.fail_immediately, \
+                      log_burst=args.log_burst, log_combine=args.log_combine, bookends=args.with_bookends, \
+                      autoremove=args.auto_remove, colors=args.colors, progress=args.progress, \
+                      debug=args.debug, verbose=args.verbose)
+
+    result = builder.build()
 
     if DEBUG_LOG:
         DEBUG_LOG.close()
 
     sys.exit(0 if result else 1)
 except (KeyboardInterrupt, SystemExit) as e:
+    if builder:
+        builder.cleanup()
+
     if type(e) == SystemExit:
         sys.exit(int(str(e)))
     else: