Merge lp:~cmiller/desktopcouch/segv-ya-rly into lp:desktopcouch

[Chad Miller]

Since replication takes a long time (and we are not clever enough yet to replicate asynchronously), all replication is pushed into a subthread so that we don't block DBus server calls on getPort and such.

However, for some GUI libraries, GUI functions are not allowed to be outside the main execution thread. Violating that causes undefined behavior.

We need access to the keyring data in replication, and 'gnomekeyring' may try to display an alert to the user, using GUI functions. Doing so from inside the replication thread, outside the main thread, can cause SEGV crashes in deep and mysterious parts of Python and libraries it uses.

Now, add a wrapper for those functions that can call GUI functions. First test what environment we're in and if in a subthread, ask the twisted reactor to run the target function in the main execution thread and return the values down to the subthread.

[Guillermo Gonzalez (verterok)]

looks good

review: Approve

[Tim Cole (tcole)]

Awesome. I'm glad we found and addressed the real problem.

review: Approve

=== modified file 'desktopcouch/replication_services/example.py'
--- desktopcouch/replication_services/example.py	2009-09-28 15:13:33 +0000
+++ desktopcouch/replication_services/example.py	2010-03-30 00:11:19 +0000
@@ -13,7 +13,9 @@
 
 # Required
 def oauth_data():
-    """OAuth information needed to replicate to a server."""
+    """OAuth information needed to replicate to a server.  This may be
+    called from a subthread, so be sure not to violate any execution 
+    idioms, like updating the GUI from a non-main thread."""
     return dict(consumer_key="", consumer_secret="", oauth_token="",
             oauth_token_secret="")
     # or to symbolize failure
 
=== modified file 'desktopcouch/replication_services/ubuntuone.py'
--- desktopcouch/replication_services/ubuntuone.py	2010-03-10 22:27:28 +0000
+++ desktopcouch/replication_services/ubuntuone.py	2010-03-30 00:11:19 +0000
@@ -17,6 +17,15 @@
 oauth_consumer_key = "ubuntuone"
 oauth_consumer_secret = "hammertime"
 
+def in_main_thread(function, *args, **kwargs):
+    from twisted.python.threadable import isInIOThread
+    if isInIOThread():  # We may not be in main thread right now.
+        from twisted.internet.threads import blockingCallFromThread
+        from twisted.internet import reactor
+        return blockingCallFromThread(reactor, function, *args, **kwargs)
+    else:  # If in main, just do it.
+        return function(*args, **kwargs)
+
 def is_active():
     """Can we deliver information?"""
     return get_oauth_data() is not None
@@ -29,7 +38,7 @@
         return oauth_data
 
     try:
-        matches = gnomekeyring.find_items_sync(
+        matches = in_main_thread(gnomekeyring.find_items_sync,
             gnomekeyring.ITEM_GENERIC_SECRET,
             {'ubuntuone-realm': "https://ubuntuone.com",
              'oauth-consumer-key': oauth_consumer_key})
@@ -58,13 +67,13 @@
 def get_oauth_token(consumer):
     """Get the token from the keyring"""
     try:
-        items = gnomekeyring.find_items_sync(
+        items = in_main_thread(gnomekeyring.find_items_sync,
             gnomekeyring.ITEM_GENERIC_SECRET,
             {'ubuntuone-realm': "https://one.ubuntu.com",
              'oauth-consumer-key': consumer.key})
     except gnomekeyring.NoMatchError:
         logging.info("No o.u.c key.  Maybe there's uo.c key?")
-        items = gnomekeyring.find_items_sync(
+        items = in_main_thread(gnomekeyring.find_items_sync,
             gnomekeyring.ITEM_GENERIC_SECRET,
             {'ubuntuone-realm': "https://ubuntuone.com",
              'oauth-consumer-key': consumer.key})