--- a/bench.py	Fri Aug 05 12:27:07 2016 +0800
+++ b/bench.py	Sun Aug 07 12:59:40 2016 +0800
@@ -265,10 +265,11 @@
     conn.close()
 
 
-def lock():
-    flags = os.O_WRONLY | os.O_CREAT | os.O_EXCL
+def lock(path):
     try:
-        return os.fdopen(os.open(LOCKFILE, flags), 'w')
+        fd = os.open(path, os.O_WRONLY | os.O_CREAT | os.O_EXCL)
+        os.write(fd, '%d' % os.getpid())
+        return fd
     except OSError as e:
         if e.errno == errno.EEXIST:
             logging.error('cannot lock data directory')
@@ -277,8 +278,15 @@
             raise
 
 
-def unlock():
-    os.remove(LOCKFILE)
+def unlock(fd, path):
+    try:
+        os.close(fd)
+        os.remove(path)
+    except OSError as e:
+        if e.errno == errno.ENOENT:
+            logging.info("lock file %r doesn't exist", path)
+        else:
+            raise
 
 
 def main(args):
@@ -287,7 +295,7 @@
     else:
         names = args.marks.split(',')
         marks = OrderedDict((k, v) for k, v in MARKS.items() if k in names)
-    lock()
+    lockfd = lock(LOCKFILE)
     try:
         dbinit()
         if args.auto:
@@ -297,7 +305,7 @@
                 args.revsets = guessnew(args.auto, marks)
         dbupdate(args.revsets, marks, args.mintime, args.mintries, args.retry)
     finally:
-        unlock()
+        unlock(lockfd, LOCKFILE)
 
 
 if __name__ == '__main__':