rcu nits

845e50fe · Nickolai Zeldovich · 31786361 · 845e50fe
--- a/rcu.c
+++ b/rcu.c
@@ -11,7 +11,7 @@
 struct rcu {
  void *item;
  unsigned long epoch;
-  struct rcu *rcu;
+  struct rcu *next;
  void (*dofree)(void *);
 };
 static struct { struct rcu *x __attribute__((aligned (CACHELINE))); } rcu_delayed_head[NCPU];
@@ -21,6 +21,8 @@ static struct { uint x __attribute__((aligned (CACHELINE))); } min_epoch[NCPU];
 static struct { struct spinlock l __attribute__((aligned (CACHELINE))); } rcu_lock[NCPU];
 static struct { int v __attribute__((aligned (CACHELINE))); } delayed_nfree[NCPU];

+enum { rcu_debug = 0 };
+
 void
 rcuinit(void)
 {
@@ -60,40 +62,50 @@ rcu_gc(void)
  for (r = rcu_delayed_head[cpu->id].x; r != NULL; r = nr) {
    if (r->epoch >= min_epoch[cpu->id].x)
      break;
-    // cprintf("free: %d\n", r->epoch);
+    // cprintf("free: %d (%x %x)\n", r->epoch, r->dofree, r->item);
    if (r->dofree == 0)
      panic("rcu_gc");
    r->dofree(r->item);
    delayed_nfree[cpu->id].v--;
    n++;
-    rcu_delayed_head[cpu->id].x = r->rcu;
+    rcu_delayed_head[cpu->id].x = r->next;
    if (rcu_delayed_head[cpu->id].x == 0)
      rcu_delayed_tail[cpu->id].x = 0;
-    nr = r->rcu;
+    nr = r->next;
    kmfree(r);
  }
  release(&rcu_lock[cpu->id].l);
+  // cprintf("rcu_gc: cpu %d n %d delayed_nfree=%d min_epoch=%d\n",
+  //         cpu->id, n, delayed_nfree[cpu->id], min_epoch[cpu->id]);
  popcli();

-  // cprintf("rcu_gc: n %d ndelayed_free=%d\n", n, delayed_nfree);
+  // global_epoch can be bumped anywhere; this seems as good a place as any
+  __sync_fetch_and_add(&global_epoch, 1);
 }

 // XXX Use atomic instruction to update list (instead of holding lock)
 void
 rcu_delayed(void *e, void (*dofree)(void *))
 {
+  if (rcu_debug) {
+    cprintf("rcu_delayed: %x %x\n", dofree, e);
+    for (struct rcu *r = rcu_delayed_head[cpu->id].x; r; r = r->next)
+      if (r->item == e && r->dofree == dofree)
+	panic("rcu_delayed double free");
+  }
+
  struct rcu *r = rcu_alloc();
  if (r == 0)
    panic("rcu_delayed");
  r->dofree = dofree;
  r->item = e;
-  r->rcu = 0;
+  r->next = 0;
  r->epoch = global_epoch;
  pushcli();
  acquire(&rcu_lock[cpu->id].l);
  // cprintf("rcu_delayed: %d\n", global_epoch);
  if (rcu_delayed_tail[cpu->id].x != 0) 
-    rcu_delayed_tail[cpu->id].x->rcu = r;
+    rcu_delayed_tail[cpu->id].x->next = r;
  rcu_delayed_tail[cpu->id].x = r;
  if (rcu_delayed_head[cpu->id].x == 0)
    rcu_delayed_head[cpu->id].x = r;
@@ -131,9 +143,6 @@ rcu_end_write(struct spinlock *l)
 {
  rcu_end_read();

-  // global_epoch can be bumped anywhere; this seems as good a place as any
-  __sync_fetch_and_add(&global_epoch, 1);
-
  if (l) release(l);
 }