homing: Fix race between joint's homing status and state machine done.

Author: BsAtHome

src/emc/motion/control.c

@@ -2122,7 +2122,19 @@ static void update_status(void)
 	}
 #endif
 	joint_status->flag = joint->flag;
-	joint_status->homing = get_homing(joint_num);
+	if(!(joint_status->homing && !get_homing(joint_num) && get_homing_is_active())) {
+		// Prevent race condition.
+		// (See also emc/motion/homing.c: base_write_homing_out_pins())
+		// The homing status variable turns false before get_homing_is_active()
+		// turns false. This means that a new homing command on a joint might
+		// fail due to the homing state machine being active while all joints
+		// already are in the 'not homing' state.
+		// Solution:
+		// Do not update the homing status when going from homing --> not homing
+		// and the state machine is still active. The homing status deassertion
+		// must be delayed until the state machine is done.
+		joint_status->homing = get_homing(joint_num);
+	}
 	joint_status->homed  = get_homed(joint_num);
 	joint_status->pos_cmd = joint->pos_cmd;
 	joint_status->pos_fb = joint->pos_fb;
@@ -2209,4 +2221,4 @@ static void update_status(void)
 	old_motion_flag = emcmotStatus->motionFlag;
     }
 #endif
-}
+}

src/emc/motion/homing.c

@@ -542,6 +542,19 @@ static void base_write_homing_out_pins(int njoints)
     one_joint_home_data_t *addr;
     for (jno = 0; jno < njoints; jno++) {
         addr = &(joint_home_data->jhd[jno]);
+        if(!(*(addr->homing) && !H[jno].homing && homing_active)) {
+            // Prevent race condition.
+            // (See also emc/motion/control.c: update_status())
+            // The homing status variable turns false before homing_active state
+            // turns false. This means that a new homing command on a joint might
+            // fail due to the homing state machine being active while all joints
+            // already are in the 'not homing' state.
+            // Solution:
+            // Do not update the homing status when going from homing --> not homing
+            // and the state machine is still active. The homing status deassertion
+            // must be delayed until the state machine is done.
+            *(addr->homing) = H[jno].homing;
+        }
         *(addr->homing)       = H[jno].homing;       // OUT
         *(addr->homed)        = H[jno].homed;        // OUT
         *(addr->home_state)   = H[jno].home_state;   // OUT