From 1f80ec402150bcc838ab2950d79a1870d0c75a6b Mon Sep 17 00:00:00 2001
From: Luca Toniolo <10792599+grandixximo@users.noreply.github.com>
Date: Thu, 15 Oct 2026 23:40:40 +1100
Subject: [PATCH] motion: a non-finite inverse in coordinated mode no longer
 hangs the servo thread

When the inverse kinematics gave a non-finite joint location in
coordinated mode, the check broke out of the joint loop only. Joint 0
was left without its interpolation point, so the enclosing
cubicNeedNextPoint() loop ran the planner and the inverse again,
forever, inside the servo thread: millions of identical errors and, on
a real-time kernel, a frozen PC. Leave the loop the way a failed
inverse already does, so the error is reported once and the machine
disables.

Reported by Sigma1912 with a mill-turn kinematics module whose inverse
divided by zero.
---
 src/emc/motion/control.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/emc/motion/control.c b/src/emc/motion/control.c
index 17fb96b7ddd..49310f752fe 100644
--- a/src/emc/motion/control.c
+++ b/src/emc/motion/control.c
@@ -1459,6 +1459,11 @@ static void get_pos_cmds(long period)
 		       this cycle so it doesn't really matter */
 		    cubicAddPoint(&(joint->cubic), joint->coarse_pos);
 		}
+		/* a non-finite joint left joint 0 without its point, so the
+		   loop would ask for it forever and hang the servo thread */
+		if (joint_num < NO_OF_KINS_JOINTS) {
+		    break;
+		}
 	    }
 	    else
 	    {