when unlocking a sequence of ranges (in crange_locked), we need to first

read the next pointer, and then unlock a node. otherwise, the next pointer changes and we try to unlock subsequent nodes that we never locked.

when unlocking a sequence of ranges (in crange_locked), we need to first
ea058e70 · Nickolai Zeldovich · 6150f2f6 · ea058e70
--- a/crange.cc
+++ b/crange.cc
@@ -119,7 +119,7 @@ range::dec_ref(void)
 range::range(crange *crarg, u64 k, u64 sz, rcu_freed *v, range *n, int nl)
  : rcu_freed("range_delayed")
 {
-  dprintf("range:range:: %lu %lu %d\n", k, sz, nl);
+  dprintf("range::range: %lu %lu %d\n", k, sz, nl);
  key = k;
  size = sz;
  value = v;
@@ -500,8 +500,12 @@ crange_locked::crange_locked(crange_locked &&x)
 crange_locked::~crange_locked()
 {
  if (prev_) {
-    for (range *e = prev_; e && e != succ_; e = e->next[0].ptr())
+    range *n;
+    for (range *e = prev_; e && e != succ_; e = n) {
+      // as soon a we release, the next pointer can change, so read it first
+      n = e->next[0].ptr();
      release(e->lock);
+    }
  }
 }