Add standardized way to post client dependent functions

Former-commit-id: fb50163b47cf660911dc7f67809c15ba1394613a

src/replication.cpp

@@ -1478,7 +1478,7 @@ void rdbPipeReadHandler(struct aeEventLoop *eventLoop, int fd, void *clientData,
              * setup write handler (and disable pipe read handler, below) */
             if (nwritten != g_pserver->rdb_pipe_bufflen) {
                 g_pserver->rdb_pipe_numconns_writing++;
-                aePostFunction(g_pserver->rgthreadvar[slave->iel].el, [conn] {
+                slave->postFunction([conn](client *) {
                     connSetWriteHandler(conn, rdbPipeWriteHandler);
                 });
             }
@@ -1607,21 +1607,7 @@ void updateSlavesWaitingBgsave(int bgsaveerr, int type)
                 }
                 else
                 {
-                    aePostFunction(g_pserver->rgthreadvar[replica->iel].el, [replica] {
-                        // Because the client could have been closed while the lambda waited to run we need to
-			            // verify the replica is still connected
-                        listIter li;
-                        listNode *ln;
-                        listRewind(g_pserver->slaves,&li);
-                        bool fFound = false;
-                        while ((ln = listNext(&li))) {
-                            if (listNodeValue(ln) == replica) {
-                                fFound = true;
-                                break;
-                            }
-                        }
-                        if (!fFound)
-                            return;
+                    replica->postFunction([](client *replica) {
                         connSetWriteHandler(replica->conn,NULL);
                         if (connSetWriteHandler(replica->conn,sendBulkToSlave) == C_ERR) {
                             freeClient(replica);

src/server.cpp

@@ -3887,6 +3887,15 @@ int processCommand(client *c, int callFlags) {
     return C_OK;
 }
 
+bool client::postFunction(std::function<void(client *)> fn) {
+    this->casyncOpsPending++;
+    return aePostFunction(g_pserver->rgthreadvar[this->iel].el, [this, fn]{
+        std::lock_guard<decltype(this->lock)> lock(this->lock);
+        --casyncOpsPending;
+        fn(this);
+    }) == AE_OK;
+}
+
 /*================================== Shutdown =============================== */
 
 /* Close listening sockets. Also unlink the unix domain socket if

src/server.h

@@ -1335,6 +1335,9 @@ typedef struct client {
     int iel; /* the event loop index we're registered with */
     struct fastlock lock;
     int master_error;
+
+    // post a function from a non-client thread to run on its client thread
+    bool postFunction(std::function<void(client *)> fn);
 } client;
 
 struct saveparam {