Fix when the master connection is disconnected, replication retry read indefinitely (#10032)

Now if redis is still loading when we receive sigterm, we will wait for the loading to reach the event
loop (once in 2mb) before actually shutting down. See #10003.

This change caused valgrind CI to fail.
See https://github.com/redis/redis/runs/4662901673?check_suite_focus=true

This pr is mainly to solve the problem that redis process cannot be exited normally.
When the master is disconnected, if repl is processing diskless loading and using `connRead` to read data from master,
it may enter an infinite retry state, which does not handle `connRead` returning 0(master connection disconnected).

(cherry picked from commit 73951abe7b86a565e3123fc1b8033efdcd1c0c04)

1 files changed, 3 insertions, 1 deletions

diff --git a/src/rio.c b/src/rio.c
index 0d107708f..d131fd222 100644
--- a/src/rio.c
+++ b/src/rio.c
@@ -211,7 +211,9 @@ static size_t rioConnRead(rio *r, void *buf, size_t len) {
         int retval = connRead(r->io.conn.conn,
                           (char*)r->io.conn.buf + sdslen(r->io.conn.buf),
                           toread);
-        if (retval <= 0) {
+        if (retval == 0) {
+            return 0;
+        } else if (retval < 0) {
             if (errno == EWOULDBLOCK) errno = ETIMEDOUT;
             return 0;
         }