Merge authors:
James Hunt (jamesodhunt)
Related merge proposals:
https://code.launchpad.net/~jamesodhunt/upstart/bug-901038/+merge/231705
proposed by: James Hunt (jamesodhunt)
review: Approve - Steve Langasek (vorlon)
------------------------------------------------------------
revno: 1664 [merge]
committer: Steve Langasek <steve.langa...@canonical.com>
branch nick: upstream
timestamp: Mon 2014-09-08 08:18:43 -0700
message:
Merge lp:~jamesodhunt/upstart/bug-901038
modified:
ChangeLog
util/telinit.c
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=== modified file 'ChangeLog'
--- ChangeLog 2014-09-04 11:07:22 +0000
+++ ChangeLog 2014-09-08 15:18:43 +0000
@@ -1,3 +1,15 @@
+2014-09-08 James Hunt <james.h...@ubuntu.com>
+
+ * util/telinit.c: Remove UPSTART_TELINIT_U_NO_WAIT check as it
+ shouldn't realistically be needed.
+
+2014-08-21 James Hunt <james.h...@ubuntu.com>
+
+ * util/telinit.c: restart_upstart():
+ - Revert to synchronous behaviour coupled with unavoidable
+ poll to ensure telinit only returns once a re-exec has
+ completed (LP: #901038).
+
2014-09-04 James Hunt <james.h...@ubuntu.com>
* NEWS: Release 1.13.2
=== modified file 'util/telinit.c'
--- util/telinit.c 2014-03-10 13:43:50 +0000
+++ util/telinit.c 2014-09-08 10:12:10 +0000
@@ -160,27 +160,73 @@
int
restart_upstart (void)
{
- nih_local NihDBusProxy *upstart = NULL;
- DBusPendingCall *ret;
+ nih_local NihDBusProxy *upstart = NULL;
+ NihError *err;
+ int ret;
upstart = upstart_open (NULL);
if (! upstart)
return -1;
- /* Fire and forget:
- *
- * Ask Upstart to restart itself using the async interface to
- * avoid the client-side complaining if and when it detects that
- * Upstart has severed all connections to perform the re-exec.
- */
- ret = upstart_restart (upstart, NULL, NULL, NULL, 0);
- dbus_connection_flush(upstart->connection);
-
- /* We don't care about the return code, but we have to keep
- * the compiler happy.
- */
- if (ret != (DBusPendingCall *)TRUE)
- return 0;
+ /* Ask Upstart to restart itself.
+ *
+ * Since it is not possible to serialise a D-Bus connection,
+ * Upstart is forced to sever all D-Bus client connections,
+ * including this one.
+ *
+ * Further, since the user expects telinit to block _until the
+ * re-exec has finished and Upstart is accepting connections
+ * once again_, the only solution is to wait for the forced
+ * disconnect, then poll until it is possible to create a new
+ * connection.
+ *
+ * Note that we don't (can't) care about the return code since
+ * it's not reliable:
+ *
+ * - either the re-exec request completed and D-Bus returned zero
+ * before Upstart started the re-exec.
+ *
+ * - or the re-exec request completed but upstart started the
+ * re-exec (severing all D-Bus connections) before D-Bus got a
+ * chance to finish cleanly meaning we receive a return of -1.
+ *
+ * We cannot know exactly what happened so have to allow for
+ * both scenarios. Note the implicit assumption that the re-exec
+ * request itself was accepted. If this assumption is incorrect
+ * (should not be possible), the worst case scenario is that
+ * upstart does not re-exec and then we quickly drop out of the
+ * reconnect block since it never went offline.
+ */
+ ret = upstart_restart_sync (NULL, upstart);
+
+ if (ret < 0) {
+ err = nih_error_get ();
+ nih_free (err);
+ }
+
+ nih_free (upstart);
+
+ nih_debug ("Waiting for upstart to finish re-exec");
+
+ /* We believe Upstart is now in the process of
+ * re-exec'ing so attempt forever to reconnect.
+ *
+ * This sounds dangerous but there is no other option,
+ * and a connection must be possible unless the system
+ * is completely broken.
+ */
+ while (TRUE) {
+
+ upstart = upstart_open (NULL);
+ if (upstart)
+ break;
+
+ err = nih_error_get ();
+ nih_free (err);
+
+ /* Avoid DoS'ing the system whilst we wait */
+ usleep (100000);
+ }
return 0;
}
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