server/process: Run idle commands in a separate idle thread

When bitbake is off running heavier "idle" commands, it doesn't service it's
command socket which means stopping/interrupting it is hard. It also means we
can't "ping" from the UI to know if it is still alive.

For those reasons, split idle command execution into it's own thread.

The commands are generally already self containted so this is easier than
expected. We do have to be careful to only handle inotify poll() from a single
thread at a time. It also means we always have to use a thread lock when sending
events since both the idle thread and the command thread may generate log messages
(and hence events). The patch depends on  previous fixes to the builtins locking
in event.py and the heartbeat enable/disable changes as well as other locking
additions.

We use a condition to signal from the idle thread when other sections of code
can continue, thanks to Joshua Watt for the review and tweaks squashed into this
patch. We do have some sync points where we need to ensure any currently executing
commands have finished before we can start a new async command for example.

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

4 files changed, 97 insertions, 50 deletions

diff --git a/lib/bb/command.py b/lib/bb/command.py
index 732327d84..0706b8927 100644
--- a/lib/bb/command.py
+++ b/lib/bb/command.py
@@ -60,7 +60,7 @@ class Command:
         # FIXME Add lock for this
         self.currentAsyncCommand = None
 
-    def runCommand(self, commandline, ro_only = False):
+    def runCommand(self, commandline, process_server, ro_only=False):
         command = commandline.pop(0)
 
         # Ensure cooker is ready for commands
@@ -84,7 +84,7 @@ class Command:
                 if not hasattr(command_method, 'readonly') or not getattr(command_method, 'readonly'):
                     return None, "Not able to execute not readonly commands in readonly mode"
             try:
-                self.cooker.process_inotify_updates()
+                self.cooker.process_inotify_updates_apply()
                 if getattr(command_method, 'needconfig', True):
                     self.cooker.updateCacheSync()
                 result = command_method(self, commandline)
@@ -100,7 +100,10 @@ class Command:
             else:
                 return result, None
         if self.currentAsyncCommand is not None:
-            return None, "Busy (%s in progress)" % self.currentAsyncCommand[0]
+            # Wait for the idle loop to have cleared (30s max)
+            process_server.wait_for_idle(timeout=30)
+            if self.currentAsyncCommand is not None:
+                return None, "Busy (%s in progress)" % self.currentAsyncCommand[0]
         if command not in CommandsAsync.__dict__:
             return None, "No such command"
         self.currentAsyncCommand = (command, commandline)
@@ -109,7 +112,7 @@ class Command:
 
     def runAsyncCommand(self):
         try:
-            self.cooker.process_inotify_updates()
+            self.cooker.process_inotify_updates_apply()
             if self.cooker.state in (bb.cooker.state.error, bb.cooker.state.shutdown, bb.cooker.state.forceshutdown):
                 # updateCache will trigger a shutdown of the parser
                 # and then raise BBHandledException triggering an exit
diff --git a/lib/bb/cooker.py b/lib/bb/cooker.py
index ded936978..a5a635858 100644
--- a/lib/bb/cooker.py
+++ b/lib/bb/cooker.py
@@ -149,7 +149,7 @@ class BBCooker:
     Manages one bitbake build run
     """
 
-    def __init__(self, featureSet=None, idleCallBackRegister=None):
+    def __init__(self, featureSet=None, idleCallBackRegister=None, waitIdle=None):
         self.recipecaches = None
         self.eventlog = None
         self.skiplist = {}
@@ -164,6 +164,7 @@ class BBCooker:
         self.configuration = bb.cookerdata.CookerConfiguration()
 
         self.idleCallBackRegister = idleCallBackRegister
+        self.waitIdle = waitIdle
 
         bb.debug(1, "BBCooker starting %s" % time.time())
         sys.stdout.flush()
@@ -220,6 +221,8 @@ class BBCooker:
         bb.debug(1, "BBCooker startup complete %s" % time.time())
         sys.stdout.flush()
 
+        self.inotify_threadlock = threading.Lock()
+
     def init_configdata(self):
         if not hasattr(self, "data"):
             self.initConfigurationData()
@@ -248,11 +251,18 @@ class BBCooker:
         self.notifier = pyinotify.Notifier(self.watcher, self.notifications)
 
     def process_inotify_updates(self):
-        for n in [self.confignotifier, self.notifier]:
-            if n and n.check_events(timeout=0):
-                # read notified events and enqueue them
-                n.read_events()
-                n.process_events()
+        with self.inotify_threadlock:
+            for n in [self.confignotifier, self.notifier]:
+                if n and n.check_events(timeout=0):
+                    # read notified events and enqueue them
+                    n.read_events()
+
+    def process_inotify_updates_apply(self):
+        with self.inotify_threadlock:
+            for n in [self.confignotifier, self.notifier]:
+                if n and n.check_events(timeout=0):
+                    n.read_events()
+                    n.process_events()
 
     def config_notifications(self, event):
         if event.maskname == "IN_Q_OVERFLOW":
@@ -1744,7 +1754,7 @@ class BBCooker:
         return
 
     def post_serve(self):
-        self.shutdown(force=True)
+        self.shutdown(force=True, idle=False)
         prserv.serv.auto_shutdown()
         if hasattr(bb.parse, "siggen"):
             bb.parse.siggen.exit()
@@ -1754,12 +1764,15 @@ class BBCooker:
         if hasattr(self, "data"):
             bb.event.fire(CookerExit(), self.data)
 
-    def shutdown(self, force = False):
+    def shutdown(self, force=False, idle=True):
         if force:
             self.state = state.forceshutdown
         else:
             self.state = state.shutdown
 
+        if idle:
+            self.waitIdle(30)
+
         if self.parser:
             self.parser.shutdown(clean=not force)
             self.parser.final_cleanup()
diff --git a/lib/bb/server/process.py b/lib/bb/server/process.py
index 2aee9ef05..ac7749d36 100644
--- a/lib/bb/server/process.py
+++ b/lib/bb/server/process.py
@@ -92,8 +92,11 @@ class ProcessServer():
         self.maxuiwait = 30
         self.xmlrpc = False
 
+        self.idle = None
+        # Need a lock for _idlefuns changes
         self._idlefuns = {}
         self._idlefuncsLock = threading.Lock()
+        self.idle_cond = threading.Condition(self._idlefuncsLock)
 
         self.bitbake_lock = lock
         self.bitbake_lock_name = lockname
@@ -151,6 +154,12 @@ class ProcessServer():
 
         return ret
 
+    def wait_for_idle(self, timeout=30):
+        # Wait for the idle loop to have cleared
+        with self.idle_cond:
+            # FIXME - the 1 is the inotify processing in cooker which always runs
+            self.idle_cond.wait_for(lambda: len(self._idlefuns) <= 1, timeout)
+
     def main(self):
         self.cooker.pre_serve()
 
@@ -174,6 +183,12 @@ class ProcessServer():
                 self.controllersock.close()
                 self.controllersock = False
             if self.haveui:
+                # Wait for the idle loop to have cleared (30s max)
+                self.wait_for_idle(30)
+                if self.cooker.command.currentAsyncCommand is not None:
+                    serverlog("Idle loop didn't finish queued commands after 30s, exiting.")
+                    self.quit = True
+
                 fds.remove(self.command_channel)
                 bb.event.unregister_UIHhandler(self.event_handle, True)
                 self.command_channel_reply.writer.close()
@@ -185,7 +200,7 @@ class ProcessServer():
                 self.cooker.clientComplete()
                 self.haveui = False
             ready = select.select(fds,[],[],0)[0]
-            if newconnections:
+            if newconnections and not self.quit:
                 serverlog("Starting new client")
                 conn = newconnections.pop(-1)
                 fds.append(conn)
@@ -257,7 +272,7 @@ class ProcessServer():
                     continue
                 try:
                     serverlog("Running command %s" % command)
-                    self.command_channel_reply.send(self.cooker.command.runCommand(command))
+                    self.command_channel_reply.send(self.cooker.command.runCommand(command, self))
                     serverlog("Command Completed (socket: %s)" % os.path.exists(self.sockname))
                 except Exception as e:
                    stack = traceback.format_exc()
@@ -285,6 +300,9 @@ class ProcessServer():
 
             ready = self.idle_commands(.1, fds)
 
+        if self.idle:
+            self.idle.join()
+
         serverlog("Exiting (socket: %s)" % os.path.exists(self.sockname))
         # Remove the socket file so we don't get any more connections to avoid races
         # The build directory could have been renamed so if the file isn't the one we created
@@ -300,7 +318,7 @@ class ProcessServer():
         self.sock.close()
 
         try:
-            self.cooker.shutdown(True)
+            self.cooker.shutdown(True, idle=False)
             self.cooker.notifier.stop()
             self.cooker.confignotifier.stop()
         except:
@@ -359,47 +377,60 @@ class ProcessServer():
                     msg.append(":\n%s" % procs)
                 serverlog("".join(msg))
 
-    def idle_commands(self, delay, fds=None):
+    def idle_thread(self):
         def remove_idle_func(function):
             with self._idlefuncsLock:
                 del self._idlefuns[function]
+                self.idle_cond.notify_all()
 
-        nextsleep = delay
-        if not fds:
+        while not self.quit:
+            nextsleep = 0.1
             fds = []
 
-        with self._idlefuncsLock:
-            items = list(self._idlefuns.items())
+            with self._idlefuncsLock:
+                items = list(self._idlefuns.items())
 
-        for function, data in items:
-            try:
-                retval = function(self, data, False)
-                if isinstance(retval, idleFinish):
-                    serverlog("Removing idle function %s at idleFinish" % str(function))
-                    remove_idle_func(function)
-                    self.cooker.command.finishAsyncCommand(retval.msg)
-                    nextsleep = None
-                elif retval is False:
-                    serverlog("Removing idle function %s" % str(function))
+            for function, data in items:
+                try:
+                    retval = function(self, data, False)
+                    if isinstance(retval, idleFinish):
+                        serverlog("Removing idle function %s at idleFinish" % str(function))
+                        remove_idle_func(function)
+                        self.cooker.command.finishAsyncCommand(retval.msg)
+                        nextsleep = None
+                    elif retval is False:
+                        serverlog("Removing idle function %s" % str(function))
+                        remove_idle_func(function)
+                        nextsleep = None
+                    elif retval is True:
+                        nextsleep = None
+                    elif isinstance(retval, float) and nextsleep:
+                        if (retval < nextsleep):
+                            nextsleep = retval
+                    elif nextsleep is None:
+                        continue
+                    else:
+                        fds = fds + retval
+                except SystemExit:
+                    raise
+                except Exception as exc:
+                    if not isinstance(exc, bb.BBHandledException):
+                        logger.exception('Running idle function')
                     remove_idle_func(function)
-                    nextsleep = None
-                elif retval is True:
-                    nextsleep = None
-                elif isinstance(retval, float) and nextsleep:
-                    if (retval < nextsleep):
-                        nextsleep = retval
-                elif nextsleep is None:
-                    continue
-                else:
-                    fds = fds + retval
-            except SystemExit:
-                raise
-            except Exception as exc:
-                if not isinstance(exc, bb.BBHandledException):
-                    logger.exception('Running idle function')
-                remove_idle_func(function)
-                serverlog("Exception %s broke the idle_thread, exiting" % traceback.format_exc())
-                self.quit = True
+                    serverlog("Exception %s broke the idle_thread, exiting" % traceback.format_exc())
+                    self.quit = True
+
+            if nextsleep is not None:
+                select.select(fds,[],[],nextsleep)[0]
+
+    def idle_commands(self, delay, fds=None):
+        nextsleep = delay
+        if not fds:
+            fds = []
+
+        if not self.idle:
+            self.idle = threading.Thread(target=self.idle_thread)
+            self.idle.start()
 
         # Create new heartbeat event?
         now = time.time()
@@ -592,7 +623,7 @@ def execServer(lockfd, readypipeinfd, lockname, sockname, server_timeout, xmlrpc
         writer = ConnectionWriter(readypipeinfd)
         try:
             featureset = []
-            cooker = bb.cooker.BBCooker(featureset, server.register_idle_function)
+            cooker = bb.cooker.BBCooker(featureset, server.register_idle_function, server.wait_for_idle)
             cooker.configuration.profile = profile
         except bb.BBHandledException:
             return None
diff --git a/lib/bb/server/xmlrpcserver.py b/lib/bb/server/xmlrpcserver.py
index 01f55538a..2e65dc34a 100644
--- a/lib/bb/server/xmlrpcserver.py
+++ b/lib/bb/server/xmlrpcserver.py
@@ -118,7 +118,7 @@ class BitBakeXMLRPCServerCommands():
         """
         Run a cooker command on the server
         """
-        return self.server.cooker.command.runCommand(command, self.server.readonly)
+        return self.server.cooker.command.runCommand(command, self.server, self.server.readonly)
 
     def getEventHandle(self):
         return self.event_handle