quick fix for slab mover deadlock

this fix may be replaced with a better restructuring; as this was done more
properly in the result handler code below. Not releasing the slab lock while
unlinking can cause a deadlock:

item A unlinks, which locks LRU, then tries to lock SLAB
page mover locks SLAB, locks item B, tries to unlink item B
if done after A locks LRU, it deadlocks while B tries to lock LRU.

doh :/

1 files changed, 2 insertions, 0 deletions

diff --git a/slabs.c b/slabs.c
index cedb1e8..6f59b17 100644
--- a/slabs.c
+++ b/slabs.c
@@ -862,7 +862,9 @@ static int slab_rebalance_move(void) {
                             // Only safe to hold slabs lock because refcount
                             // can't drop to 0 until we release item lock.
                             STORAGE_delete(storage, it);
+                            pthread_mutex_unlock(&slabs_lock);
                             do_item_unlink(it, hv);
+                            pthread_mutex_lock(&slabs_lock);
                         }
                         status = MOVE_BUSY;
                     } else {