lock.py: fix Exception handling

Before, when logdir is not writable, _try_lock will raise an Exception
like "Permission denied: '/var/log/log_lock.pid'", and in this case,
_unlock_thread will not be called and the variable count will not be
handled, it maybe cause log_lock.pid not be deleted in case like [1].

For [1], it is an cross compile case, when dnf install some packages to
rootfs, seems like some threads don't do chroot like work, some threads
do chroot like work. so for the threads don't do chroot, "Permission denied"
Exception happend, for the threads that do chroot, log_lock.pid will be
created under installroot/var/log/log_lock.pid, since variable count not
handled correct before, log_lock.pid may not be deleted correctly.

So fixed like this, if _try_lock raise Exception, _unlock_thread first,
then raise the Exception.

[1] #1963

Signed-off-by: Changqing Li <[email protected]>

dnf/lock.py

@@ -128,7 +128,11 @@ def __enter__(self):
         self._lock_thread()
         prev_pid = -1
         my_pid = os.getpid()
-        pid = self._try_lock(my_pid)
+        try:
+            pid = self._try_lock(my_pid)
+        except Exception:
+            self._unlock_thread()
+            raise
         while pid != my_pid:
             if pid != -1:
                 if not self.blocking:
@@ -140,7 +144,11 @@ def __enter__(self):
                     logger.info(msg)
                     prev_pid = pid
             time.sleep(1)
-            pid = self._try_lock(my_pid)
+            try:
+                pid = self._try_lock(my_pid)
+            except Exception:
+                self._unlock_thread()
+                raise
 
     def __exit__(self, *exc_args):
         if self.count == 1: