From 740e59ea20f4ebfa80c889966daf6f7ed07c70fb Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Thu, 31 Jul 2025 15:52:41 -0400
Subject: kernel: socket: Block if cmsg queue is empty

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/kern/kern_socket.c | 7 +++++++
 1 file changed, 7 insertions(+)

(limited to 'sys')

diff --git a/sys/kern/kern_socket.c b/sys/kern/kern_socket.c
index 42f31d9..065245b 100644
--- a/sys/kern/kern_socket.c
+++ b/sys/kern/kern_socket.c
@@ -32,6 +32,7 @@
 #include <sys/systm.h>
 #include <sys/proc.h>
 #include <sys/namei.h>
+#include <sys/sched.h>
 #include <sys/errno.h>
 #include <sys/syslog.h>
 #include <sys/filedesc.h>
@@ -477,6 +478,12 @@ recvmsg(int socket, struct msghdr *msg, int flags)
     clp = &ksock->cmsg_list;
     cmsg = TAILQ_FIRST(&clp->list);
 
+    /* Empty? */
+    while (cmsg == NULL) {
+        sched_yield();
+        cmsg = TAILQ_FIRST(&clp->list);
+    }
+
     while (cmsg != NULL) {
         cmsghdr = &cmsg->hdr;
 
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