1 files changed, 97 insertions, 0 deletions
diff --git a/unionfs/update.c b/unionfs/update.c
new file mode 100644
index 00000000..8ec66883
--- /dev/null
+++ b/unionfs/update.c
@@ -0,0 +1,97 @@
+/* Hurd unionfs
+   Copyright (C) 2005 Free Software Foundation, Inc.
+   Written by Gianluca Guida <glguida@gmail.com>.
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License as
+   published by the Free Software Foundation; either version 2 of the
+   License, or * (at your option) any later version.
+ 
+   This program is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+ 
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+   USA.  */
+
+/* Update thread: A clean way to solve locking issues of 
+   root node update.  */
+
+#define _GNU_SOURCE
+
+#include <errno.h>
+#include <string.h>
+#include <cthreads.h>
+#include <rwlock.h>
+
+#include "ncache.h"
+#include "node.h"
+#include "ulfs.h"
+
+/* Reader lock is used by threads that are going to
+   add/remove an ulfs; writer lock is hold by the 
+   update thread.  */
+static struct rwlock update_rwlock;
+static struct condition update_wakeup;
+static struct mutex update_lock;
+
+static void
+_root_update_thread ()
+{
+  error_t err;
+  
+  while (1)
+    {
+      if (hurd_condition_wait (&update_wakeup, &update_lock))
+	mutex_unlock (&update_lock);
+
+      rwlock_writer_lock (&update_rwlock);
+
+      do 
+	{
+	  ulfs_check();
+	  err = node_init_root (netfs_root_node);
+	}
+      while (err == ENOENT);
+
+      if (err)
+	{
+	  fprintf (stderr, "update thread: got a %s\n", strerror (err));
+	}
+
+      ncache_reset ();
+
+      rwlock_writer_unlock (&update_rwlock);
+    }
+}
+
+void
+root_update_schedule ()
+{
+  condition_signal (&update_wakeup);
+}
+
+void
+root_update_disable ()
+{
+  rwlock_reader_lock (&update_rwlock);
+}
+
+void
+root_update_enable ()
+{
+  rwlock_reader_unlock (&update_rwlock);
+}
+
+void
+root_update_init()
+{
+  mutex_init (&update_lock);
+  rwlock_init (&update_rwlock);
+  condition_init (&update_wakeup);
+
+  cthread_detach (cthread_fork ( (cthread_fn_t)_root_update_thread, 0));
+}