lock: include Linux pid namespace identifier in prefix
Previously, the lock only contains a hostname as an attempt to detect pid
namespace difference. However, that's not enough on modern Linux - a single
hostname could have different pid namespaces.
That means if people run hg inside different PID namespaces with a same UTS
namespae, the lock would be broken - an hg proccess in pid namespace A will
think the lock having a "random" pid in pid namespace B is "dead" and remove
it.
This patch solves the above issue by appending an PID namespace identifier of
the current process to the lock prefix ("hostname"). It depends on /proc
being mounted properly. But I don't think there is a better way to get pid
namespace identifier reliably.
--- a/mercurial/lock.py Fri Feb 10 13:35:21 2017 -0800
+++ b/mercurial/lock.py Fri Feb 10 13:56:31 2017 -0800
@@ -9,12 +9,14 @@
import contextlib
import errno
+import os
import socket
import time
import warnings
from . import (
error,
+ pycompat,
util,
)
@@ -22,9 +24,17 @@
"""Return a string which is used to differentiate pid namespaces
It's useful to detect "dead" processes and remove stale locks with
- confidence. Typically it's just hostname.
+ confidence. Typically it's just hostname. On modern linux, we include an
+ extra Linux-specific pid namespace identifier.
"""
- return socket.gethostname()
+ result = socket.gethostname()
+ if pycompat.sysplatform.startswith('linux'):
+ try:
+ result += '/%x' % os.stat('/proc/self/ns/pid').st_ino
+ except OSError as ex:
+ if ex.errno not in (errno.ENOENT, errno.EACCES, errno.ENOTDIR):
+ raise
+ return result
class lock(object):
'''An advisory lock held by one process to control access to a set