Object locks use events

Instead of calling custom hooks from object locks, we use standard event
sending mechanism to inform protocols about object lock changes. As
event sending is lockless, the unlocking protocol simply enqueues the
appropriate event to the given loop when the locking is done.

nest/locks.c

@@ -37,7 +37,11 @@
 #include "nest/iface.h"
 
 static list olock_list;
-static event *olock_event;
+
+DEFINE_DOMAIN(attrs);
+static DOMAIN(attrs) olock_domain;
+#define OBJ_LOCK	LOCK_DOMAIN(attrs, olock_domain)
+#define OBJ_UNLOCK	UNLOCK_DOMAIN(attrs, olock_domain)
 
 static inline int
 olock_same(struct object_lock *x, struct object_lock *y)
@@ -54,35 +58,52 @@ olock_same(struct object_lock *x, struct object_lock *y)
 static void
 olock_free(resource *r)
 {
-  struct object_lock *q, *l = (struct object_lock *) r;
+  /* Called externally from rfree() */
+  struct object_lock *l = SKIP_BACK(struct object_lock, r, r);
   node *n;
 
+  OBJ_LOCK;
   DBG("olock: Freeing %p\n", l);
   switch (l->state)
     {
     case OLOCK_STATE_FREE:
       break;
     case OLOCK_STATE_LOCKED:
-    case OLOCK_STATE_EVENT:
+      /* Remove myself from the olock_list */
       rem_node(&l->n);
+
+      /* Maybe the notification is still pending. */
+      ev_postpone(&l->event);
+
+      /* Get new lock candidate */
       n = HEAD(l->waiters);
-      if (n->next)
+      if (NODE_VALID(n))
 	{
-	  DBG("olock: -> %p becomes locked\n", n);
-	  q = SKIP_BACK(struct object_lock, n, n);
+	  struct object_lock *q = SKIP_BACK(struct object_lock, n, n);
+
+	  /* Remove this candidate from waiters list */
 	  rem_node(n);
+
+	  /* Move waiter lists */
+	  DBG("olock: -> %p becomes locked\n", n);
 	  add_tail_list(&q->waiters, &l->waiters);
-	  q->state = OLOCK_STATE_EVENT;
+
+	  /* Add the new olock to olock_list */
 	  add_head(&olock_list, n);
-	  ev_schedule(olock_event);
+
+	  /* Inform */
+	  q->state = OLOCK_STATE_LOCKED;
+	  ev_send(q->target, &q->event);
 	}
       break;
     case OLOCK_STATE_WAITING:
+      /* Remove from the waiters list */
       rem_node(&l->n);
       break;
     default:
       ASSERT(0);
     }
+  OBJ_UNLOCK;
 }
 
 static void
@@ -140,6 +161,8 @@ olock_acquire(struct object_lock *l)
   node *n;
   struct object_lock *q;
 
+  OBJ_LOCK;
+
   WALK_LIST(n, olock_list)
     {
       q = SKIP_BACK(struct object_lock, n, n);
@@ -148,36 +171,19 @@ olock_acquire(struct object_lock *l)
 	  l->state = OLOCK_STATE_WAITING;
 	  add_tail(&q->waiters, &l->n);
 	  DBG("olock: %p waits\n", l);
+
+	  OBJ_UNLOCK;
 	  return;
 	}
     }
+
   DBG("olock: %p acquired immediately\n", l);
-  l->state = OLOCK_STATE_EVENT;
   add_head(&olock_list, &l->n);
-  ev_schedule(olock_event);
-}
 
-static void
-olock_run_event(void *unused UNUSED)
-{
-  node *n;
-  struct object_lock *q;
+  l->state = OLOCK_STATE_LOCKED;
+  ev_send(l->target, &l->event);
 
-  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);
-    }
+  OBJ_UNLOCK;
 }
 
 /**
@@ -191,5 +197,5 @@ olock_init(void)
 {
   DBG("olock: init\n");
   init_list(&olock_list);
-  olock_event = ev_new_init(&root_pool, olock_run_event, NULL);
+  olock_domain = DOMAIN_NEW(attrs, "Object lock");
 }

nest/locks.h

@@ -31,8 +31,8 @@ struct object_lock {
   uint inst;		/* ... instance ID */
   struct iface *iface;	/* ... interface */
   struct iface *vrf;	/* ... or VRF (if iface is unknown) */
-  void (*hook)(struct object_lock *);	/* Called when the lock succeeds */
-  void *data;		/* User data */
+  event event;		/* Enqueued when the lock succeeds */
+  event_list *target;	/* Where to put the event */
   /* ... internal to lock manager, don't touch ... */
   node n;		/* Node in list of olocks */
   int state;		/* OLOCK_STATE_xxx */
@@ -50,6 +50,5 @@ void olock_init(void);
 #define OLOCK_STATE_FREE 0
 #define OLOCK_STATE_LOCKED 1
 #define OLOCK_STATE_WAITING 2
-#define OLOCK_STATE_EVENT 3		/* waiting for unlock processing */
 
 #endif

proto/babel/babel.c

@@ -1761,9 +1761,9 @@ babel_find_iface(struct babel_proto *p, struct iface *what)
 }
 
 static void
-babel_iface_locked(struct object_lock *lock)
+babel_iface_locked(void *_ifa)
 {
-  struct babel_iface *ifa = lock->data;
+  struct babel_iface *ifa = _ifa;
   struct babel_proto *p = ifa->proto;
 
   if (!babel_open_socket(ifa))
@@ -1818,8 +1818,11 @@ babel_add_iface(struct babel_proto *p, struct iface *new, struct babel_iface_con
   lock->addr = IP6_BABEL_ROUTERS;
   lock->port = ifa->cf->port;
   lock->iface = ifa->iface;
-  lock->hook = babel_iface_locked;
-  lock->data = ifa;
+  lock->event = (event) {
+    .hook = babel_iface_locked,
+    .data = ifa,
+  };
+  lock->target = &global_event_list;
 
   olock_acquire(lock);
 }

proto/bgp/bgp.c

@@ -1528,9 +1528,9 @@ bgp_feed_end(struct channel *C)
 
 
 static void
-bgp_start_locked(struct object_lock *lock)
+bgp_start_locked(void *_p)
 {
-  struct bgp_proto *p = lock->data;
+  struct bgp_proto *p = _p;
   const struct bgp_config *cf = p->cf;
 
   if (p->p.proto_state != PS_START)
@@ -1637,8 +1637,11 @@ bgp_start(struct proto *P)
   lock->iface = p->cf->iface;
   lock->vrf = p->cf->iface ? NULL : p->p.vrf;
   lock->type = OBJLOCK_TCP;
-  lock->hook = bgp_start_locked;
-  lock->data = p;
+  lock->event = (event) {
+    .hook = bgp_start_locked,
+    .data = p,
+  };
+  lock->target = &global_event_list;
 
   /* For dynamic BGP, we use inst 1 to avoid collisions with regular BGP */
   if (bgp_is_dynamic(p))

proto/ospf/iface.c

@@ -484,9 +484,9 @@ ospf_iface_find(struct ospf_proto *p, struct iface *what)
 }
 
 static void
-ospf_iface_add(struct object_lock *lock)
+ospf_iface_add(void *_ifa)
 {
-  struct ospf_iface *ifa = lock->data;
+  struct ospf_iface *ifa = _ifa;
   struct ospf_proto *p = ifa->oa->po;
 
   /* Open socket if interface is not stub */
@@ -668,8 +668,11 @@ ospf_iface_new(struct ospf_area *oa, struct ifa *addr, struct ospf_iface_patt *i
   lock->port = OSPF_PROTO;
   lock->inst = ifa->instance_id;
   lock->iface = iface;
-  lock->data = ifa;
-  lock->hook = ospf_iface_add;
+  lock->event = (event) {
+    .hook = ospf_iface_add,
+    .data = ifa,
+  };
+  lock->target = &global_event_list;
 
   olock_acquire(lock);
 }

proto/radv/radv.c

@@ -266,9 +266,9 @@ radv_iface_find(struct radv_proto *p, struct iface *what)
 }
 
 static void
-radv_iface_add(struct object_lock *lock)
+radv_iface_add(void *_ifa)
 {
-  struct radv_iface *ifa = lock->data;
+  struct radv_iface *ifa = _ifa;
   struct radv_proto *p = ifa->ra;
 
   if (! radv_sk_open(ifa))
@@ -305,8 +305,11 @@ radv_iface_new(struct radv_proto *p, struct iface *iface, struct radv_iface_conf
   lock->type = OBJLOCK_IP;
   lock->port = ICMPV6_PROTO;
   lock->iface = iface;
-  lock->data = ifa;
-  lock->hook = radv_iface_add;
+  lock->event = (event) {
+    .hook = radv_iface_add,
+    .data = ifa,
+  };
+  lock->target = &global_event_list;
   ifa->lock = lock;
 
   olock_acquire(lock);

proto/rip/rip.c

@@ -667,9 +667,9 @@ rip_iface_update_bfd(struct rip_iface *ifa)
 
 
 static void
-rip_iface_locked(struct object_lock *lock)
+rip_iface_locked(void *_ifa)
 {
-  struct rip_iface *ifa = lock->data;
+  struct rip_iface *ifa = _ifa;
   struct rip_proto *p = ifa->rip;
 
   if (!rip_open_socket(ifa))
@@ -731,8 +731,11 @@ rip_add_iface(struct rip_proto *p, struct iface *iface, struct rip_iface_config
   lock->type = OBJLOCK_UDP;
   lock->port = ic->port;
   lock->iface = iface;
-  lock->data = ifa;
-  lock->hook = rip_iface_locked;
+  lock->event = (event) {
+    .hook = rip_iface_locked,
+    .data = ifa,
+  };
+  lock->target = &global_event_list;
   ifa->lock = lock;
 
   olock_acquire(lock);