Lock free usecount better debuggability

diff --git a/lib/lockfree.h b/lib/lockfree.h
index abb426760e56dd2fcf5d8b0f5d3b66482c275e49..23ab3523763735a3f7b74164380088ae68cc70d5 100644 (file)
--- a/lib/lockfree.h
+++ b/lib/lockfree.h
@@ -30,12 +30,13 @@ struct lfuc {
  * lfuc_lock - increase an atomic usecount
  * @c: the usecount structure
  */
-static inline void lfuc_lock(struct lfuc *c)
+static inline u64 lfuc_lock(struct lfuc *c)
 {
   /* Locking is trivial; somebody already holds the underlying data structure
    * so we just increase the use count. Nothing can be freed underneath our hands. */
   u64 uc = atomic_fetch_add_explicit(&c->uc, 1, memory_order_acq_rel);
   ASSERT_DIE(uc > 0);
+  return uc & (LFUC_IN_PROGRESS - 1);
 }
 
 /**
@@ -47,9 +48,10 @@ static inline void lfuc_lock(struct lfuc *c)
  * Handy for situations with flapping routes. Use only from the same
  * loop as which runs the prune routine.
  */
-static inline void lfuc_lock_revive(struct lfuc *c)
+static inline u64 lfuc_lock_revive(struct lfuc *c)
 {
-  UNUSED u64 uc = atomic_fetch_add_explicit(&c->uc, 1, memory_order_acq_rel);
+  u64 uc = atomic_fetch_add_explicit(&c->uc, 1, memory_order_acq_rel);
+  return uc & (LFUC_IN_PROGRESS - 1);
 }
 
 /**
@@ -61,7 +63,7 @@ static inline void lfuc_lock_revive(struct lfuc *c)
  * If the usecount reaches zero, a prune event is run to possibly free the object.
  * The prune event MUST use lfuc_finished() to check the object state.
  */
-static inline void lfuc_unlock(struct lfuc *c, event_list *el, event *ev)
+static inline u64 lfuc_unlock(struct lfuc *c, event_list *el, event *ev)
 {
   /* Unlocking is tricky. We do it lockless so at the same time, the prune
    * event may be running, therefore if the unlock gets us to zero, it must be
@@ -102,11 +104,13 @@ static inline void lfuc_unlock(struct lfuc *c, event_list *el, event *ev)
 
   /* And now, finally, simultaneously pop the in-progress indicator and the
    * usecount, possibly allowing the pruning routine to free this structure */
-  atomic_fetch_sub_explicit(&c->uc, LFUC_IN_PROGRESS + 1, memory_order_acq_rel);
+  uc = atomic_fetch_sub_explicit(&c->uc, LFUC_IN_PROGRESS + 1, memory_order_acq_rel);
 
   /* ... and to reduce the load a bit, the pruning routine will better wait for
    * RCU synchronization instead of a busy loop. */
   rcu_read_unlock();
+
+  return uc - LFUC_IN_PROGRESS - 1;
 }
 
 /**

diff --git a/lib/netindex.c b/lib/netindex.c
index 3194c77b219acf64031d3d6ae1b46dbaca4675b6..b6eb07a0c8d00bca43bb687de7e688b6bd46248c 100644 (file)
--- a/lib/netindex.c
+++ b/lib/netindex.c
@@ -189,13 +189,13 @@ net_new_index_locked(struct netindex_hash_private *hp, const net_addr *n, pool *
 void net_lock_index(netindex_hash *h UNUSED, struct netindex *i)
 {
 //  log(L_TRACE "Lock index %p", i);
-  return lfuc_lock(&i->uc);
+  lfuc_lock(&i->uc);
 }
 
 void net_unlock_index(netindex_hash *h, struct netindex *i)
 {
 //  log(L_TRACE "Unlock index %p", i);
-  return lfuc_unlock(&i->uc, h->cleanup_list, &h->cleanup_event);
+  lfuc_unlock(&i->uc, h->cleanup_list, &h->cleanup_event);
 }
 
 struct netindex *