Added universal locking mechanism which will solve problems

with protocols wanting to use the same port on the same interface
during reconfiguration time.

How to use locks: In the if_notify hook, just order locks for the
interfaces you want to work with and do the real socket opening after the
lock hook function gets called. When you stop using the socket, close
it and rfree() the lock.

Please update your protocols to use the new locking mechanism.

1 files changed, 147 insertions, 0 deletions

diff --git a/nest/locks.c b/nest/locks.c
new file mode 100644
index 00000000..a2134fb6
--- /dev/null
+++ b/nest/locks.c
@@ -0,0 +1,147 @@
+/*
+ *	BIRD Object Locks
+ *
+ *	(c) 1999 Martin Mares <mj@ucw.cz>
+ *
+ *	Can be freely distributed and used under the terms of the GNU GPL.
+ */
+
+#include <stdio.h>
+
+#define LOCAL_DEBUG
+
+#include "nest/bird.h"
+#include "lib/resource.h"
+#include "nest/locks.h"
+#include "nest/iface.h"
+
+static list olock_list;
+static event *olock_event;
+
+static inline int
+olock_same(struct object_lock *x, struct object_lock *y)
+{
+  return
+    x->type == y->type &&
+    x->iface == y->iface &&
+    x->port == y->port &&
+    ipa_equal(x->addr, y->addr);
+}
+
+static void
+olock_free(resource *r)
+{
+  struct object_lock *q, *l = (struct object_lock *) r;
+  node *n;
+
+  DBG("olock: Freeing %p\n", l);
+  switch (l->state)
+    {
+    case OLOCK_STATE_FREE:
+      break;
+    case OLOCK_STATE_LOCKED:
+    case OLOCK_STATE_EVENT:
+      rem_node(&l->n);
+      n = HEAD(l->waiters);
+      if (n->next)
+	{
+	  DBG("olock: -> %p becomes locked\n", n);
+	  q = SKIP_BACK(struct object_lock, n, n);
+	  rem_node(n);
+	  add_tail_list(&l->waiters, &q->waiters);
+	  q->state = OLOCK_STATE_EVENT;
+	  add_head(&olock_list, n);
+	  ev_schedule(olock_event);
+	}
+      break;
+    case OLOCK_STATE_WAITING:
+      rem_node(&l->n);
+      break;
+    default:
+      ASSERT(0);
+    }
+}
+
+static void
+olock_dump(resource *r)
+{
+  struct object_lock *l = (struct object_lock *) r;
+  static char *olock_states[] = { "free", "locked", "waiting", "event" };
+
+  debug("(%d:%s:%I:%d) [%s]", l->type, (l->iface ? l->iface->name : "?"), l->addr, l->port, olock_states[l->state]);
+  if (!EMPTY_LIST(l->waiters))
+    debug(" [wanted]\n");
+}
+
+static struct resclass olock_class = {
+  "ObjLock",
+  sizeof(struct object_lock),
+  olock_free,
+  olock_dump
+};
+
+struct object_lock *
+olock_new(pool *p)
+{
+  struct object_lock *l = ralloc(p, &olock_class);
+
+  l->state = OLOCK_STATE_FREE;
+  init_list(&l->waiters);
+  return l;
+}
+
+void
+olock_acquire(struct object_lock *l)
+{
+  node *n;
+  struct object_lock *q;
+
+  WALK_LIST(n, olock_list)
+    {
+      q = SKIP_BACK(struct object_lock, n, n);
+      if (olock_same(q, l))
+	{
+	  l->state = OLOCK_STATE_WAITING;
+	  add_tail(&q->waiters, &l->n);
+	  DBG("olock: %p waits\n", l);
+	  return;
+	}
+    }
+  DBG("olock: %p acquired immediately\n", l);
+  l->state = OLOCK_STATE_EVENT;
+  add_head(&olock_list, &l->n);
+  ev_schedule(olock_event);
+}
+
+int
+olock_run_event(void *unused)
+{
+  node *n;
+  struct object_lock *q;
+
+  DBG("olock: Processing events\n");
+  for(;;)
+    {
+      n = HEAD(olock_list);
+      if (!n->next)
+	break;
+      q = SKIP_BACK(struct object_lock, n, n);
+      if (q->state != OLOCK_STATE_EVENT)
+	break;
+      DBG("olock: %p locked\n", q);
+      q->state = OLOCK_STATE_LOCKED;
+      rem_node(&q->n);
+      add_tail(&olock_list, &q->n);
+      q->hook(q);
+    }
+  return 0;
+}
+
+void
+olock_init(void)
+{
+  DBG("olock: init\n");
+  init_list(&olock_list);
+  olock_event = ev_new(&root_pool);
+  olock_event->hook = olock_run_event;
+}