More robust handling of AOF rewrite child.

After the wait3() syscall we used to do something like that:

    if (pid == server.rdb_child_pid) {
        backgroundSaveDoneHandler(exitcode,bysignal);
    } else {
        ....
    }

So the AOF rewrite was handled in the else branch without actually
checking if the pid really matches. This commit makes the check explicit
and logs at WARNING level if the pid returned by wait3() does not match
neither the RDB or AOF rewrite child.

1 files changed, 5 insertions, 1 deletions

diff --git a/src/redis.c b/src/redis.c
index 87f5e812f..b42fac354 100644
--- a/src/redis.c
+++ b/src/redis.c
@@ -902,8 +902,12 @@ int serverCron(struct aeEventLoop *eventLoop, long long id, void *clientData) {
 
             if (pid == server.rdb_child_pid) {
                 backgroundSaveDoneHandler(exitcode,bysignal);
-            } else {
+            } else if (pid == server.aof_child_pid) {
                 backgroundRewriteDoneHandler(exitcode,bysignal);
+            } else {
+                redisLog(REDIS_WARNING,
+                    "Warning, detected child with unmatched pid: %ld",
+                    (long)pid);
             }
             updateDictResizePolicy();
         }