Merge pull request #3024 from michalgregor/master

Added QMutex protection to write_output as a workaround for issue #2251

spyderlib/widgets/externalshell/baseshell.py

@@ -16,7 +16,7 @@
 
 # Third party imports
 from qtpy.QtCore import (QByteArray, QProcess, Qt, QTextCodec, QTimer,
-                         Signal, Slot)
+                         Signal, Slot, QMutex)
 from qtpy.QtWidgets import (QHBoxLayout, QInputDialog, QLabel, QLineEdit,
                             QMenu, QToolButton, QVBoxLayout, QWidget)
 
@@ -62,6 +62,9 @@ def __init__(self, parent=None, fname=None, wdir=None,
         QWidget.__init__(self, parent)
 
         self.menu_actions = menu_actions
+        self.write_lock = QMutex()
+        self.buffer_lock = QMutex()
+        self.buffer = []
 
         self.run_button = None
         self.kill_button = None
@@ -293,10 +296,30 @@ def get_stderr(self):
         return self.transcode(qba)
 
     def write_output(self):
+        # if we are already writing something else,
+        # store the present message in a buffer
+        if not self.write_lock.tryLock():
+            self.buffer_lock.lock()
+            self.buffer.append(self.get_stdout())
+            self.buffer_lock.unlock()
+
+            if not self.write_lock.tryLock():
+                return
+
         self.shell.write(self.get_stdout(), flush=True)
-        # Commenting the line below improves crashes on long
-        # output. See Issue 2251
-        # QApplication.processEvents()
+
+        while True:
+            self.buffer_lock.lock()
+            messages = self.buffer
+            self.buffer = []
+
+            if not messages:
+                self.write_lock.unlock()
+                self.buffer_lock.unlock()
+                return
+
+            self.buffer_lock.unlock()
+            self.shell.write("\n".join(messages), flush=True)
 
     def send_to_process(self, qstr):
         raise NotImplementedError