Repair async rehash code removed by merge

Former-commit-id: 14a3ab8133c474bf8f1ad636c8699d5d59c5394e

src/ae.cpp

@@ -814,7 +814,9 @@ int aeThreadOwnsLock()
 
 int aeLockContested(int threshold)
 {
-    return g_lock.m_ticket.m_active < static_cast<uint16_t>(g_lock.m_ticket.m_avail - threshold);
+    ticket ticketT;
+    __atomic_load(&g_lock.m_ticket.u, &ticketT.u, __ATOMIC_RELAXED);
+    return ticketT.m_active < static_cast<uint16_t>(ticketT.m_avail - threshold);
 }
 
 int aeLockContention()

src/dict.cpp

@@ -350,6 +350,7 @@ int dictTryExpand(dict *d, unsigned long size, bool fShrink) {
 int dictRehash(dict *d, int n) {
     int empty_visits = n*10; /* Max number of empty buckets to visit. */
     if (!dictIsRehashing(d)) return 0;
+    if (d->asyncdata) return 0;
 
     while(n-- && d->ht[0].used != 0) {
         dictEntry *de, *nextde;
@@ -694,7 +695,7 @@ static dictEntry *dictGenericDelete(dict *d, const void *key, int nofree) {
                 if (!nofree) {
                     if (table == 0 && d->asyncdata != nullptr && (ssize_t)idx < d->rehashidx) {
                         he->next = d->asyncdata->deGCList;
-                        d->asyncdata->deGCList = he->next;
+                        d->asyncdata->deGCList = he;
                     } else {
                         dictFreeKey(d, he);
                         dictFreeVal(d, he);
@@ -750,9 +751,14 @@ dictEntry *dictUnlink(dict *ht, const void *key) {
 void dictFreeUnlinkedEntry(dict *d, dictEntry *he) {
     if (he == NULL) return;
 
-    dictFreeKey(d, he);
-    dictFreeVal(d, he);
-    zfree(he);
+    if (d->asyncdata) {
+        he->next = d->asyncdata->deGCList;
+        d->asyncdata->deGCList = he;
+    } else { 
+        dictFreeKey(d, he);
+        dictFreeVal(d, he);
+        zfree(he);
+    }
 }
 
 /* Destroy an entire dictionary */

src/server.cpp

@@ -2059,6 +2059,11 @@ bool expireOwnKeys()
     return false;
 }
 
+int hash_spin_worker() {
+    auto ctl = serverTL->rehashCtl;
+    return dictRehashSomeAsync(ctl, 1);
+}
+
 /* This function handles 'background' operations we are required to do
  * incrementally in Redis databases, such as active key expiring, resizing,
  * rehashing. */
@@ -2154,6 +2159,12 @@ void databasesCron(bool fMainThread) {
             }
         }
     }
+
+    if (serverTL->rehashCtl) {
+        setAeLockSetThreadSpinWorker(hash_spin_worker);
+    } else {
+        setAeLockSetThreadSpinWorker(nullptr);
+    }
 }
 
 /* We take a cached value of the unix time in the global state because with