Replaced lock file code with flock()

Author: expobrain

git/util.py

@@ -4,6 +4,7 @@
 # This module is part of GitPython and is released under
 # the BSD License: http://www.opensource.org/licenses/bsd-license.php
 
+from fcntl import flock, LOCK_UN, LOCK_EX, LOCK_NB
 import os
 import re
 import sys
@@ -324,12 +325,12 @@ def update(self, op_code, cur_count, max_count=None, message=''):
 
         You may read the contents of the current line in self._cur_line"""
         pass
-        
+
 
 class CallableRemoteProgress(RemoteProgress):
     """An implementation forwarding updates to any callable"""
     __slots__ = ('_callable')
-    
+
     def __init__(self, fn):
         self._callable = fn
         super(CallableRemoteProgress, self).__init__()
@@ -535,9 +536,10 @@ class LockFile(object):
     As we are a utility class to be derived from, we only use protected methods.
 
     Locks will automatically be released on destruction"""
-    __slots__ = ("_file_path", "_owns_lock")
+    __slots__ = ("_file_path", "_owns_lock", "_file_descriptor")
 
     def __init__(self, file_path):
+        self._file_descriptor = None
         self._file_path = file_path
         self._owns_lock = False
 
@@ -559,17 +561,24 @@ def _obtain_lock_or_raise(self):
         :raise IOError: if a lock was already present or a lock file could not be written"""
         if self._has_lock():
             return
+
         lock_file = self._lock_file_path()
-        if os.path.isfile(lock_file):
-            raise IOError("Lock for file %r did already exist, delete %r in case the lock is illegal" %
-                          (self._file_path, lock_file))
+
+        # Create lock file
+        try:
+            open(lock_file, 'a').close()
+        except OSError as e:
+            # Silence error only if file exists
+            if e.errno != 17:  # 17 -> File exists
+                raise
 
         try:
-            fd = os.open(lock_file, os.O_WRONLY | os.O_CREAT | os.O_EXCL, 0)
-            os.close(fd)
+            fd = os.open(lock_file, os.O_WRONLY, 0)
+            flock(fd, LOCK_EX | LOCK_NB)
         except OSError as e:
             raise IOError(str(e))
 
+        self._file_descriptor = fd
         self._owns_lock = True
 
     def _obtain_lock(self):
@@ -582,19 +591,15 @@ def _release_lock(self):
         if not self._has_lock():
             return
 
-        # if someone removed our file beforhand, lets just flag this issue
-        # instead of failing, to make it more usable.
-        lfp = self._lock_file_path()
-        try:
-            # on bloody windows, the file needs write permissions to be removable.
-            # Why ...
-            if os.name == 'nt':
-                os.chmod(lfp, 0o777)
-            # END handle win32
-            os.remove(lfp)
-        except OSError:
-            pass
+        fd = self._file_descriptor
+        lock_file = self._lock_file_path()
+
+        flock(fd, LOCK_UN)
+        os.close(fd)
+        os.remove(lock_file)
+
         self._owns_lock = False
+        self._file_descriptor = None
 
 
 class BlockingLockFile(LockFile):
@@ -629,7 +634,7 @@ def _obtain_lock(self):
             try:
                 super(BlockingLockFile, self)._obtain_lock()
             except IOError:
-                # synity check: if the directory leading to the lockfile is not
+                # sanity check: if the directory leading to the lockfile is not
                 # readable anymore, raise an execption
                 curtime = time.time()
                 if not os.path.isdir(os.path.dirname(self._lock_file_path())):