[inotify] Fix Observer.unschedule hang on linux when called with wa…

…tch of an unmounted path (#869)

* Stop InotifyBuffer thread on IN_IGNORE event on the "root" watch descriptor

* Added a test

* Updated changelog

* Not adding IN_IGNORE events to the queue no matter their source path, as was done until now

* Fixed formatting issues

* Trying to fix the CI by running mount and umount as root

* Update changelog

changelog.rst

@@ -12,6 +12,7 @@ Changelog
 - [watchmedo] Fix broken parsing of ``--kill-after`` argument for the ``auto-restart`` command. (`#870 <https://github.com/gorakhargosh/watchdog/issues/870>`_)
 - [watchmedo] Fix broken parsing of boolean arguments. (`#855 <https://github.com/gorakhargosh/watchdog/issues/855>`_)
 - [watchmedo] Fix broken parsing of commands from ``auto-restart``, and ``shell-command``. (`#855 <https://github.com/gorakhargosh/watchdog/issues/855>`_)
+- [inotify] Fix hang when unscheduling watch on a path in an unmounted filesystem. (`#869 <https://github.com/gorakhargosh/watchdog/pull/869>`_)
 - Thanks to our beloved contributors: @taleinat, @kianmeng, @palfrey, @IlayRosenberg, @BoboTiG
 
 2.1.7

src/watchdog/observers/inotify_buffer.py

@@ -88,6 +88,13 @@ def run(self):
             inotify_events = self._inotify.read_events()
             grouped_events = self._group_events(inotify_events)
             for inotify_event in grouped_events:
+                if not isinstance(inotify_event, tuple) and inotify_event.is_ignored:
+                    if inotify_event.src_path == self._inotify.path:
+                        # Watch was removed explicitly (inotify_rm_watch(2)) or automatically (file
+                        # was deleted, or filesystem was unmounted), stop watching for events
+                        deleted_self = True
+                    continue
+
                 # Only add delay for unmatched move_from events
                 delay = not isinstance(inotify_event, tuple) and inotify_event.is_moved_from
                 self._queue.put(inotify_event, delay)

src/watchdog/observers/inotify_c.py

@@ -323,7 +323,6 @@ def _recursive_simulate(src_path):
                     path = self._path_for_wd.pop(wd)
                     if self._wd_for_path[path] == wd:
                         del self._wd_for_path[path]
-                    continue
 
                 event_list.append(inotify_event)
 

tests/shell.py

@@ -123,3 +123,11 @@ def msize(path):
     with open(path, 'w') as w:
         w.write('0')
     os.utime(path, (0, 0))
+
+
+def mount_tmpfs(path):
+    os.system(f'sudo mount -t tmpfs none {path}')
+
+
+def unmount(path):
+    os.system(f'sudo umount {path}')

tests/test_inotify_buffer.py

@@ -25,7 +25,7 @@
 
 from watchdog.observers.inotify_buffer import InotifyBuffer
 
-from .shell import mkdir, touch, mv, rm
+from .shell import mkdir, touch, mv, rm, mount_tmpfs, unmount
 
 
 def wait_for_move_event(read_event):
@@ -116,6 +116,22 @@ def test_delete_watched_directory(p):
     inotify.close()
 
 
+@pytest.mark.timeout(5)
+def test_unmount_watched_directory_filesystem(p):
+    mkdir(p('dir1'))
+    mount_tmpfs(p('dir1'))
+    mkdir(p('dir1/dir2'))
+    inotify = InotifyBuffer(p('dir1/dir2').encode())
+    unmount(p('dir1'))
+
+    # Wait for the event to be picked up
+    inotify.read_event()
+
+    # Ensure InotifyBuffer shuts down cleanly without raising an exception
+    inotify.close()
+    assert not inotify.is_alive()
+
+
 def test_close_should_terminate_thread(p):
     inotify = InotifyBuffer(p('').encode(), recursive=True)
     assert inotify.is_alive()