Don't support Gopher if enable io threads to read queries (#7851)

There's currently an issue with IO threads and gopher (issuing lookupKey from within the thread).
simply fix is to just not support it for now.

(cherry picked from commit 9bdef76f8e3bbfaacf0962ab1ceded1bafa80bda)

redis.conf

@@ -1519,8 +1519,11 @@ notify-keyspace-events ""
 #
 # So use the 'requirepass' option to protect your instance.
 #
-# To enable Gopher support uncomment the following line and set
-# the option from no (the default) to yes.
+# Note that Gopher is not currently supported when 'io-threads-do-reads'
+# is enabled.
+#
+# To enable Gopher support, uncomment the following line and set the option
+# from no (the default) to yes.
 #
 # gopher-enabled no
 
@@ -1860,4 +1863,3 @@ jemalloc-bg-thread yes
 #
 # Set bgsave child process to cpu affinity 1,10,11
 # bgsave_cpulist 1,10-11
-

src/networking.c

@@ -1884,8 +1884,9 @@ void processInputBuffer(client *c) {
         if (c->reqtype == PROTO_REQ_INLINE) {
             if (processInlineBuffer(c) != C_OK) break;
             /* If the Gopher mode and we got zero or one argument, process
-             * the request in Gopher mode. */
-            if (server.gopher_enabled &&
+             * the request in Gopher mode. To avoid data race, Redis won't
+             * support Gopher if enable io threads to read queries. */
+            if (server.gopher_enabled && !server.io_threads_do_reads &&
                 ((c->argc == 1 && ((char*)(c->argv[0]->ptr))[0] == '/') ||
                   c->argc == 0))
             {