[bitbake-devel] [PATCH 2/4] cooker: Ensure we handle inotify before running the next command

[Richard Purdie]

The inotify watch events are handled "at idle" which could in theory mean
a command could run before any preceeding inotify events have been processed.
This leads to a theoretical race window where those events may have a
signficicant effect on the command.

Add a mechanism to allow us to ensure all pending events are processed before
running commands.

Signed-off-by: Richard Purdie <richard.purdie at linuxfoundation.org>
---
 lib/bb/command.py |  2 ++
 lib/bb/cooker.py  | 17 ++++++++++-------
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/lib/bb/command.py b/lib/bb/command.py
index c44c7a6..a923245 100644
--- a/lib/bb/command.py
+++ b/lib/bb/command.py
@@ -78,6 +78,7 @@ class Command:
                 if not hasattr(command_method, 'readonly') or False == getattr(command_method, 'readonly'):
                     return None, "Not able to execute not readonly commands in readonly mode"
             try:
+                self.cooker.process_inotify_updates()
                 if getattr(command_method, 'needconfig', False):
                     self.cooker.updateCacheSync()
                 result = command_method(self, commandline)
@@ -98,6 +99,7 @@ class Command:
 
     def runAsyncCommand(self):
         try:
+            self.cooker.process_inotify_updates()
             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 ea4df26..77b7f3d 100644
--- a/lib/bb/cooker.py
+++ b/lib/bb/cooker.py
@@ -205,15 +205,11 @@ class BBCooker:
 
         self.inotify_modified_files = []
 
-        def _process_inotify_updates(server, notifier_list, abort):
-            for n in notifier_list:
-                if n.check_events(timeout=0):
-                    # read notified events and enqeue them
-                    n.read_events()
-                    n.process_events()
+        def _process_inotify_updates(server, cooker, abort):
+            cooker.process_inotify_updates()
             return 1.0
 
-        self.configuration.server_register_idlecallback(_process_inotify_updates, [self.confignotifier, self.notifier])
+        self.configuration.server_register_idlecallback(_process_inotify_updates, self)
 
         # TOSTOP must not be set or our children will hang when they output
         try:
@@ -241,6 +237,13 @@ class BBCooker:
             os.write(readypipe, b"ready")
             os.close(readypipe)
 
+    def process_inotify_updates(self):
+        for n in [self.confignotifier, self.notifier]:
+            if n.check_events(timeout=0):
+                # read notified events and enqeue them
+                n.read_events()
+                n.process_events()
+
     def config_notifications(self, event):
         if event.maskname == "IN_Q_OVERFLOW":
             bb.warn("inotify event queue overflowed, invalidating caches.")
-- 
2.7.4