From 0d3ddc10f22ac84b0edcc33c4d12692ba2446ba1 Mon Sep 17 00:00:00 2001
From: Luca Toniolo <10792599+grandixximo@users.noreply.github.com>
Date: Fri, 7 Aug 2026 10:35:47 +0800
Subject: [PATCH] linuxcncrsh: Fix race between SET JOINT_HOME and SET
 JOINT_WAIT_HOMED

SET JOINT_HOME is acknowledged when task has received the command, but the motion controller raises the homing flag only after its next servo-thread run and the status needs to propagate back through task. A SET JOINT_WAIT_HOMED issued in between was refused with 'not homed and not in the process of homing', and the following homing commands then failed with 'Homing not possible until current homing process is finished'. This showed up as intermittent tests/linuxcncrsh failures on slow CI runners.

SET JOINT_HOME now waits for the requested joint to become homing or homed, one heartbeat at a time, the same way SET MACHINE and SET ESTOP wait for the motion controller to catch up, and refuses the command if homing never starts. A homed joint may legitimately not enter the homing state again (HOME_NO_REHOME), hence the check for either state. Home-all (-1) is excluded because joints without HOME_SEQUENCE are skipped by design. SET JOINT_WAIT_HOMED keeps a grace wait for the homing flag before declaring the error, since the homing may have been started through a different user interface.
---
 src/emc/usr_intf/emcrsh.cc | 43 +++++++++++++++++++++++++++++++++++---
 1 file changed, 40 insertions(+), 3 deletions(-)

diff --git a/src/emc/usr_intf/emcrsh.cc b/src/emc/usr_intf/emcrsh.cc
index a97ba8ad967..c50b7643fa9 100644
--- a/src/emc/usr_intf/emcrsh.cc
+++ b/src/emc/usr_intf/emcrsh.cc
@@ -63,7 +63,8 @@ using namespace linuxcnc;
 // Maximum wait time in WAIT_HEARTBEAT to see real-time move along
 #define WAIT_HEARTBEAT_TIMEOUT 1.0
 
-// Maximum number of heartbeats to wait for EMC_TASK_STATE to change
+// Maximum number of heartbeats to wait for the motion controller to catch
+// up and reflect a requested state change in the status
 #define WAIT_TASK_STATE_CHANGE_MAX 25
 
 typedef enum { cmdUnknown, cmdHello, cmdSet, cmdGet, cmdQuit, cmdShutdown, cmdHelp } cmdType;
@@ -875,8 +876,23 @@ static cmdResponseType setJointWaitHomed(connectionRecType &ctx)
 		return rtError;
 	}
 	if (joint >= 0 && !emcStatus->motion.joint[joint].homing && !emcStatus->motion.joint[joint].homed) {
-		errornl(ctx, fmt::format("Joint '{}' is not homed and not in the process of homing.", joint));
-		return rtError;
+		// The motion controller needs a servo-thread run to raise the
+		// homing flag after a 'SET JOINT_HOME' was acknowledged.
+		for (unsigned toc = 0; toc < WAIT_TASK_STATE_CHANGE_MAX; toc++) {
+			updateStatus(); // Get fresh value about joint status
+			if (emcStatus->motion.joint[joint].homing || emcStatus->motion.joint[joint].homed)
+				break;
+			// Wait for the motion control to run
+			if (rtOk != doWaitHeartbeat(ctx, 1, WAIT_HEARTBEAT_TIMEOUT)) {
+				// Bad sign,... can't wait for a heartbeat
+				errornl(ctx, "Waiting for motion controller heartbeat while running 'SET JOINT_WAIT_HOMED' failed");
+				return rtError;
+			}
+		}
+		if (!emcStatus->motion.joint[joint].homing && !emcStatus->motion.joint[joint].homed) {
+			errornl(ctx, fmt::format("Joint '{}' is not homed and not in the process of homing.", joint));
+			return rtError;
+		}
 	}
 
 	double timeout = JOINT_WAIT_HOMED_TIMEOUT;
@@ -1382,6 +1398,27 @@ static cmdResponseType setJointHome(connectionRecType &ctx)
 	}
 	if (sendHome(joint))
 		return rtError;
+
+	if (joint >= 0) {
+		// The motion controller needs a servo-thread run to raise the
+		// homing flag. Wait for it so that a following command, like
+		// 'SET JOINT_WAIT_HOMED', can rely on the state being visible.
+		// Note: a homed joint may not enter the homing state again
+		// (HOME_NO_REHOME), hence the check for either state.
+		for (unsigned toc = 0; toc < WAIT_TASK_STATE_CHANGE_MAX; toc++) {
+			// Wait for the motion control to run
+			if (rtOk != doWaitHeartbeat(ctx, 1, WAIT_HEARTBEAT_TIMEOUT)) {
+				// Bad sign,... can't wait for a heartbeat
+				errornl(ctx, "Waiting for motion controller heartbeat while running 'SET JOINT_HOME' failed");
+				return rtError;
+			}
+			updateStatus();
+			if (emcStatus->motion.joint[joint].homing || emcStatus->motion.joint[joint].homed)
+				return rtOk;
+		}
+		errornl(ctx, fmt::format("Joint '{}' did not start homing", joint));
+		return rtError;
+	}
 	return rtOk;
 }