From 0748e07a739e3db2a90aa915edea02d0b26b5bdf Mon Sep 17 00:00:00 2001
From: appel_c <christian.appel@psi.ch>
Date: Thu, 25 Jun 2026 08:53:13 +0200
Subject: [PATCH] fix(mcs): fix mcs card monitor thread

---
 .../devices/epics/mcs_card/mcs_card_csaxs.py  | 57 ++++++++++---------
 1 file changed, 30 insertions(+), 27 deletions(-)

diff --git a/csaxs_bec/devices/epics/mcs_card/mcs_card_csaxs.py b/csaxs_bec/devices/epics/mcs_card/mcs_card_csaxs.py
index 7f31e1b..b50cb06 100644
--- a/csaxs_bec/devices/epics/mcs_card/mcs_card_csaxs.py
+++ b/csaxs_bec/devices/epics/mcs_card/mcs_card_csaxs.py
@@ -454,33 +454,36 @@ class MCSCardCSAXS(PSIDeviceBase, MCSCard):
         NOTE! This logic currently works for any step scan, but has to be extended for fly scans.
         """
         while not self._scan_done_thread_kill_event.is_set():
-            while self._start_monitor_async_data_emission.wait():
-                try:
-                    if (
-                        hasattr(self.scan_parameters, "num_points")
-                        and self.scan_parameters.num_points is not None
-                    ):
-                        if self.scan_parameters.scan_type == "software_triggered":
-                            logger.info(
-                                f"Software triggered scan: {self._current_data_index}/{self.scan_parameters.num_points} points received."
-                            )
-                            if self._current_data_index == self.scan_parameters.num_points:
-                                for callback in self._scan_done_callbacks:
-                                    callback(exception=None)
-                        else:
-                            if self._current_data_index >= 1:
-                                for callback in self._scan_done_callbacks:
-                                    callback(exception=None)
-
-                    time.sleep(0.02)  # 20ms delay to avoid busy loop
-                except Exception as exc:  # pylint: disable=broad-except
-                    content = traceback.format_exc()
-                    logger.error(
-                        f"Exception in monitoring thread of complete for {self.name}:\n{content}"
-                        "Running callbacks to avoid deadlock."
-                    )
-                    for callback in self._scan_done_callbacks:
-                        callback(exception=exc)
+            # 20ms delay to avoid busy loop
+            if not self._start_monitor_async_data_emission.wait(timeout=0.02):
+                continue  # Wait for the event to be set before checking data emission
+            try:
+                if (
+                    hasattr(self.scan_parameters, "num_points")
+                    and self.scan_parameters.num_points is not None
+                ):
+                    if self.scan_parameters.scan_type == "software_triggered":
+                        logger.info(
+                            f"Software triggered scan: {self._current_data_index}/{self.scan_parameters.num_points} points received."
+                        )
+                        if self._current_data_index == self.scan_parameters.num_points:
+                            for callback in self._scan_done_callbacks:
+                                callback(exception=None)
+                    else:
+                        if self._current_data_index >= 1:
+                            for callback in self._scan_done_callbacks:
+                                callback(exception=None)
+                # 20ms delay to avoid busy loop
+                if self._scan_done_thread_kill_event.wait(timeout=0.02):
+                    continue
+            except Exception as exc:  # pylint: disable=broad-except
+                content = traceback.format_exc()
+                logger.error(
+                    f"Exception in monitoring thread of complete for {self.name}:\n{content}"
+                    "Running callbacks to avoid deadlock."
+                )
+                for callback in self._scan_done_callbacks:
+                    callback(exception=exc)
 
     def _status_callback(self, status: StatusBase, exception=None) -> None:
         """Callback for status completion."""