Fix for issue #391.

Use a simple protocol between clientsCron() and helper functions to
understand if the client is still valind and clientsCron() should
continue processing or if the client was freed and we should continue
with the next one.

src/redis.c

@@ -628,7 +628,8 @@ long long getOperationsPerSecond(void) {
     return sum / REDIS_OPS_SEC_SAMPLES;
 }
 
-void clientsCronHandleTimeout(redisClient *c) {
+/* Check for timeouts. Returns non-zero if the client was terminated */
+int clientsCronHandleTimeout(redisClient *c) {
     time_t now = server.unixtime;
 
     if (server.maxidletime &&
@@ -641,17 +642,21 @@ void clientsCronHandleTimeout(redisClient *c) {
     {
         redisLog(REDIS_VERBOSE,"Closing idle client");
         freeClient(c);
+        return 1;
     } else if (c->flags & REDIS_BLOCKED) {
         if (c->bpop.timeout != 0 && c->bpop.timeout < now) {
             addReply(c,shared.nullmultibulk);
             unblockClientWaitingData(c);
         }
     }
+    return 0;
 }
 
 /* The client query buffer is an sds.c string that can end with a lot of
- * free space not used, this function reclaims space if needed. */
-void clientsCronResizeQueryBuffer(redisClient *c) {
+ * free space not used, this function reclaims space if needed.
+ *
+ * The funciton always returns 0 as it never terminates the client. */
+int clientsCronResizeQueryBuffer(redisClient *c) {
     size_t querybuf_size = sdsAllocSize(c->querybuf);
     time_t idletime = server.unixtime - c->lastinteraction;
 
@@ -670,6 +675,7 @@ void clientsCronResizeQueryBuffer(redisClient *c) {
     /* Reset the peak again to capture the peak memory usage in the next
      * cycle. */
     c->querybuf_peak = 0;
+    return 0;
 }
 
 void clientsCron(void) {
@@ -693,8 +699,11 @@ void clientsCron(void) {
         listRotate(server.clients);
         head = listFirst(server.clients);
         c = listNodeValue(head);
-        clientsCronHandleTimeout(c);
-        clientsCronResizeQueryBuffer(c);
+        /* The following functions do different service checks on the client.
+         * The protocol is that they return non-zero if the client was
+         * terminated. */
+        if (clientsCronHandleTimeout(c)) continue;
+        if (clientsCronResizeQueryBuffer(c)) continue;
     }
 }