cooker: roll our own process pool

This fixes the hang issue encountered with parse errors. The underlying issue
seems to have been the pool.terminate(). This sends SIGTERM to each of the
multiprocessing pool's processes, however, a python process terminating in
this fashion can corrupt any queues it's interacting with, causing a number of
problems for us (e.g. the queue that sends events to the UI).

So instead of using multiprocessing's pool, we roll our own, with the ability
to cancel the work. In the very long term, the python concurrent.futures
module introduced in python 3.2 could be used to resolve this as well.

(Bitbake rev: 7c39cfd8e060cca8753ac4114775447b18e13067)

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/cooker.py

@@ -36,6 +36,7 @@ from functools import wraps
 from collections import defaultdict
 import bb, bb.exceptions, bb.command
 from bb import utils, data, parse, event, cache, providers, taskdata, runqueue
+import Queue
 import prserv.serv
 
 logger      = logging.getLogger("BitBake")
@@ -1402,20 +1403,87 @@ class ParsingFailure(Exception):
         self.recipe = recipe
         Exception.__init__(self, realexception, recipe)
 
-def parse_file(task):
-    filename, appends, caches_array = task
-    try:
-        return True, bb.cache.Cache.parse(filename, appends, parse_file.cfg, caches_array)
-    except Exception as exc:
-        tb = sys.exc_info()[2]
-        exc.recipe = filename
-        exc.traceback = list(bb.exceptions.extract_traceback(tb, context=3))
-        raise exc
-    # Need to turn BaseExceptions into Exceptions here so we gracefully shutdown
-    # and for example a worker thread doesn't just exit on its own in response to
-    # a SystemExit event for example.
-    except BaseException as exc:
-        raise ParsingFailure(exc, filename)
+class Feeder(multiprocessing.Process):
+    def __init__(self, jobs, to_parsers, quit):
+        self.quit = quit
+        self.jobs = jobs
+        self.to_parsers = to_parsers
+        multiprocessing.Process.__init__(self)
+
+    def run(self):
+        while True:
+            try:
+                quit = self.quit.get_nowait()
+            except Queue.Empty:
+                pass
+            else:
+                if quit == 'cancel':
+                    self.to_parsers.cancel_join_thread()
+                break
+
+            try:
+                job = self.jobs.pop()
+            except IndexError:
+                break
+
+            try:
+                self.to_parsers.put(job, timeout=0.5)
+            except Queue.Full:
+                self.jobs.insert(0, job)
+                continue
+
+class Parser(multiprocessing.Process):
+    def __init__(self, jobs, results, quit, init):
+        self.jobs = jobs
+        self.results = results
+        self.quit = quit
+        self.init = init
+        multiprocessing.Process.__init__(self)
+
+    def run(self):
+        if self.init:
+            self.init()
+
+        pending = []
+        while True:
+            try:
+                self.quit.get_nowait()
+            except Queue.Empty:
+                pass
+            else:
+                self.results.cancel_join_thread()
+                break
+
+            if pending:
+                result = pending.pop()
+            else:
+                try:
+                    job = self.jobs.get(timeout=0.25)
+                except Queue.Empty:
+                    continue
+
+                if job is None:
+                    break
+                result = self.parse(*job)
+
+            try:
+                self.results.put(result, timeout=0.25)
+            except Queue.Full:
+                pending.append(result)
+
+    def parse(self, filename, appends, caches_array):
+        try:
+            return True, bb.cache.Cache.parse(filename, appends, self.cfg, caches_array)
+        except Exception as exc:
+            tb = sys.exc_info()[2]
+            exc.recipe = filename
+            exc.traceback = list(bb.exceptions.extract_traceback(tb, context=3))
+            return True, exc
+        # Need to turn BaseExceptions into Exceptions here so we gracefully shutdown
+        # and for example a worker thread doesn't just exit on its own in response to
+        # a SystemExit event for example.
+        except BaseException as exc:
+            return True, ParsingFailure(exc, filename)
 
 class CookerParser(object):
     def __init__(self, cooker, filelist, masked):
@@ -1452,22 +1520,28 @@ class CookerParser(object):
         self.start()
 
     def start(self):
-        def init(cfg):
-            parse_file.cfg = cfg
-            multiprocessing.util.Finalize(None, bb.codeparser.parser_cache_save, args=(self.cooker.configuration.data, ), exitpriority=1)
-
         self.results = self.load_cached()
-
+        self.processes = []
         if self.toparse:
             bb.event.fire(bb.event.ParseStarted(self.toparse), self.cfgdata)
+            def init():
+                Parser.cfg = self.cfgdata
+                multiprocessing.util.Finalize(None, bb.codeparser.parser_cache_save, args=(self.cfgdata,), exitpriority=1)
 
-            self.pool = multiprocessing.Pool(self.num_processes, init, [self.cfgdata])
-            parsed = self.pool.imap(parse_file, self.willparse)
-            self.pool.close()
+            self.feeder_quit = multiprocessing.Queue(maxsize=1)
+            self.parser_quit = multiprocessing.Queue(maxsize=self.num_processes)
+            self.jobs = multiprocessing.Queue(maxsize=self.num_processes)
+            self.result_queue = multiprocessing.Queue()
+            self.feeder = Feeder(self.willparse, self.jobs, self.feeder_quit)
+            self.feeder.start()
+            for i in range(1, self.num_processes):
+                parser = Parser(self.jobs, self.result_queue, self.parser_quit, init)
+                parser.start()
+                self.processes.append(parser)
 
-            self.results = itertools.chain(self.results, parsed)
+            self.results = itertools.chain(self.results, self.parse_generator())
 
-    def shutdown(self, clean=True):
+    def shutdown(self, clean=True, force=False):
         if not self.toparse:
             return
 
@@ -1477,9 +1551,22 @@ class CookerParser(object):
                                             self.virtuals, self.error,
                                             self.total)
             bb.event.fire(event, self.cfgdata)
+            self.feeder_quit.put(None)
+            for process in self.processes:
+                self.jobs.put(None)
         else:
-            self.pool.terminate()
-        self.pool.join()
+            self.feeder_quit.put('cancel')
+
+            self.parser_quit.cancel_join_thread()
+            for process in self.processes:
+                self.parser_quit.put(None)
+
+            self.jobs.cancel_join_thread()
+            sys.exit(1)
+
+        for process in self.processes:
+            process.join()
+        self.feeder.join()
 
         sync = threading.Thread(target=self.bb_cache.sync)
         sync.start()
@@ -1491,6 +1578,22 @@ class CookerParser(object):
             cached, infos = self.bb_cache.load(filename, appends, self.cfgdata)
             yield not cached, infos
 
+    def parse_generator(self):
+        while True:
+            if self.parsed >= self.toparse:
+                break
+
+            try:
+                result = self.result_queue.get(timeout=0.25)
+            except Queue.Empty:
+                pass
+            else:
+                value = result[1]
+                if isinstance(value, BaseException):
+                    raise value
+                else:
+                    yield result
+
     def parse_next(self):
         try:
             parsed, result = self.results.next()