diff --git a/hgext3rd/extutil.py b/hgext3rd/extutil.py
--- a/hgext3rd/extutil.py
+++ b/hgext3rd/extutil.py
@@ -9,12 +9,10 @@
 
 import contextlib
 import errno
-import fcntl
 import os
 import subprocess
 import time
 
-from mercurial.i18n import _
 from mercurial import (
     error,
     lock as lockmod,
@@ -136,45 +134,6 @@
         return cls
     return wrap
 
-class fcntllock(object):
-    """A fcntllock based lock object. Currently it is always non-blocking.
-
-    Note that since it is fcntllock based, you can accidentally take it multiple
-    times within one process and the first one to be released will release all
-    of them. So the caller needs to be careful to not create more than one
-    instance per lock.
-    """
-    def __init__(self, opener, name, description):
-        self.path = opener.join(name)
-        self.description = description
-        self.fp = None
-
-    def __enter__(self):
-        path = self.path
-        if self.fp is not None:
-            raise error.Abort(_("unable to re-enter lock '%s'") % path)
-        try:
-            self.fp = open(path, 'w+')
-        except (IOError, OSError) as ex:
-            raise error.Abort(_("unable to create lock file '%s': %s") %
-                              (path, str(ex)))
-
-        try:
-            fcntl.lockf(self.fp, fcntl.LOCK_EX | fcntl.LOCK_NB)
-        except IOError:
-            self.fp.close()
-            self.fp = None
-            raise error.LockHeld(errno.EAGAIN, path, self.description, '')
-
-        return self
-
-    def __exit__(self, type, value, traceback):
-        fp = self.fp
-        if fp is not None:
-            fcntl.lockf(fp, fcntl.LOCK_UN)
-            fp.close()
-            self.fp = None
-
 @contextlib.contextmanager
 def flock(lockpath, description, timeout=-1):
     """A flock based lock object. Currently it is always non-blocking.
diff --git a/remotefilelog/debugcommands.py b/remotefilelog/debugcommands.py
--- a/remotefilelog/debugcommands.py
+++ b/remotefilelog/debugcommands.py
@@ -20,7 +20,7 @@
 )
 from .repack import repacklockvfs
 from .lz4wrapper import lz4decompress
-import hashlib, os, time
+import hashlib, os
 
 def debugremotefilelog(ui, path, **opts):
     decompress = opts.get('decompress')
@@ -360,12 +360,8 @@
             short(p2node), short(linknode), copyfrom))
 
 def debugwaitonrepack(repo):
-    while True:
-        try:
-            with extutil.fcntllock(repacklockvfs(repo), 'repacklock', ''):
-                return
-        except error.LockHeld:
-            time.sleep(0.1)
+    with extutil.flock(repacklockvfs(repo).join('repacklock'), ''):
+        return
 
 def debugwaitonprefetch(repo):
     with repo._lock(repo.svfs, "prefetchlock", True, None,
diff --git a/remotefilelog/repack.py b/remotefilelog/repack.py
--- a/remotefilelog/repack.py
+++ b/remotefilelog/repack.py
@@ -1,7 +1,7 @@
 from __future__ import absolute_import
 
 import os
-from hgext3rd.extutil import runshellcommand, fcntllock
+from hgext3rd.extutil import runshellcommand, flock
 from mercurial import (
     error,
     extensions,
@@ -440,8 +440,8 @@
     def run(self, targetdata, targethistory):
         ledger = repackledger()
 
-        with fcntllock(repacklockvfs(self.repo), "repacklock",
-                       _('repacking %s') % self.repo.origroot):
+        with flock(repacklockvfs(self.repo).join("repacklock"),
+                   _('repacking %s') % self.repo.origroot, timeout=0):
             self.repo.hook('prerepack')
 
             # Populate ledger from source
diff --git a/tests/test-extutil.py b/tests/test-extutil.py
--- a/tests/test-extutil.py
+++ b/tests/test-extutil.py
@@ -52,12 +52,13 @@
         except OSError as ex:
             self.assertEqual(ex.errno, errno.EACCES)
 
-    def testfcntllock(self):
+    def testflock(self):
         testtmp = os.environ["TESTTMP"]
         opener = vfs.vfs(testtmp)
         name = 'testlock'
 
-        with extutil.fcntllock(opener, name, 'testing a lock'):
+        with extutil.flock(opener.join(name), 'testing a lock',
+                           timeout=0):
             otherlock = self.otherprocesslock(opener, name)
             self.assertEquals(otherlock, locktimeout,
                               "other process should not have taken the lock")
@@ -70,7 +71,8 @@
         pid = os.fork()
         if pid == 0:
             try:
-                with extutil.fcntllock(opener, name, 'other process lock'):
+                with extutil.flock(opener.join(name), 'other process lock',
+                                   timeout=0):
                     os._exit(locksuccess)
             except error.LockHeld:
                 os._exit(locktimeout)