Merge lp:~jamesodhunt/libnih/inotify-overflow-fix into lp:libnih/1.0

[James Hunt]

* nih/watch.c: nih_watch_reader(): Handle situation where kernel
  is generating events faster than can be consumed by simply
  ignoring them. Failure to do so results in an assertion failure in
  nih_watch_handle_by_wd() since the inotify_event object will
  contain an invalid watch descriptor (-1).

Note that running the shell script below will cause Upstart to crash (generally within 60 seconds with a reasonable system) as a result of this bug:

  while [ : ]
  do
    touch /etc/init/*
  done

Unmerged revisions

1049. By James Hunt on 2011-04-26

* nih/watch.c: nih_watch_reader(): Handle situation where kernel
  is generating events faster than can be consumed by simply
  ignoring them. Failure to do so results in an assertion failure in
  nih_watch_handle_by_wd() since the inotify_event object will
  contain an invalid watch descriptor (-1).

=== modified file 'ChangeLog'
--- ChangeLog	2010-12-23 22:06:15 +0000
+++ ChangeLog	2011-04-26 15:51:42 +0000
@@ -1,3 +1,11 @@
[phone]  James Hunt <[e-mail]>
+
+	* nih/watch.c: nih_watch_reader(): Handle situation where kernel
+	  is generating events faster than can be consumed by simply
+	  ignoring them. Failure to do so results in an assertion failure in
+	  nih_watch_handle_by_wd() since the inotify_event object will
+	  contain an invalid watch descriptor (-1).
+
 2010-12-23  Scott James Remnant  <[e-mail]>
 
 	* configure.ac: Bump version to 1.0.4
 
=== modified file 'nih/watch.c'
--- nih/watch.c	2011-01-06 09:28:39 +0000
+++ nih/watch.c	2011-04-26 15:51:42 +0000
@@ -424,6 +424,13 @@
 		if (len < sz)
 			goto finish;
 
+		/* Handle situation where kernel is generating events faster
+		 * than can be consumed. Inotify will (somewhat ironically)
+		 * generate an event to signify this, so ignore it.
+		 */
+		if (event->mask & IN_Q_OVERFLOW)
+			goto consume;
+
 		/* Find the handle for this watch */
 		handle = nih_watch_handle_by_wd (watch, event->wd);
 		if (handle)
@@ -437,6 +444,7 @@
 		if (caught_free)
 			return;
 
+consume:
 		/* Remove the event from the front of the buffer, and
 		 * decrease our own length counter.
 		 */