##// END OF EJS Templates
lock: fix race in lock-breaking code...
lock: fix race in lock-breaking code With low frequency, I see hg pulls fail with output like: abort: no such file or directory: .hg/store/lock I think what happens is, in lock.py, in: def _testlock(self, locker): if not self._lockshouldbebroken(locker): return locker # if locker dead, break lock. must do this with another lock # held, or can race and break valid lock. try: with lock(self.vfs, self.f + b'.break', timeout=0): self.vfs.unlink(self.f) except error.LockError: return locker if a lock is breakable on disk, and two hg processes concurrently get to the "if locker dead" comment, a possible interleaving is: process1 finishes executing the function and then process2 finishes executing the function. If that happens, process2 will either get ENOENT in self.vfs.unlink (resulting in the spurious failure above), or break a valid lock and potentially cause repository corruption. The fix is simple enough: make sure the lock is breakable _inside_ the critical section, because only then can we know that no other process can invalidate our knowledge on the lock on disk. I don't think there are tests for this. I've tested this manually with: diff --git a/mercurial/lock.py b/mercurial/lock.py --- a/mercurial/lock.py +++ b/mercurial/lock.py @@ -351,6 +351,8 @@ class lock(object): if not self._lockshouldbebroken(locker): return locker + import random + time.sleep(1. + random.random()) # if locker dead, break lock. must do this with another lock # held, or can race and break valid lock. try: @@ -358,6 +360,7 @@ class lock(object): self.vfs.unlink(self.f) except error.LockError: return locker + time.sleep(1) def testlock(self): """return id of locker if lock is valid, else None. and I see this change of behavior before/after this commit: $ $hg init repo $ cd repo $ ln -s $HOSTNAME/effffffc:987654321 .hg/wlock $ touch a $ $hg commit -Am_ & $hg commit -Am _; wait -abort: No such file or directory: '/tmp/repo/.hg/wlock' adding a +warning: ignoring unknown working parent 679a8959a8ca! +nothing changed Differential Revision: https://phab.mercurial-scm.org/D7199

File last commit:

r43812:2fe6121c default
r44108:039fbd14 default
Show More
scmposix.py
97 lines | 2.6 KiB | text/x-python | PythonLexer
from __future__ import absolute_import
import array
import errno
import fcntl
import os
import sys
from .pycompat import getattr
from . import (
encoding,
pycompat,
util,
)
# BSD 'more' escapes ANSI color sequences by default. This can be disabled by
# $MORE variable, but there's no compatible option with Linux 'more'. Given
# OS X is widely used and most modern Unix systems would have 'less', setting
# 'less' as the default seems reasonable.
fallbackpager = b'less'
def _rcfiles(path):
rcs = [os.path.join(path, b'hgrc')]
rcdir = os.path.join(path, b'hgrc.d')
try:
rcs.extend(
[
os.path.join(rcdir, f)
for f, kind in util.listdir(rcdir)
if f.endswith(b".rc")
]
)
except OSError:
pass
return rcs
def systemrcpath():
path = []
if pycompat.sysplatform == b'plan9':
root = b'lib/mercurial'
else:
root = b'etc/mercurial'
# old mod_python does not set sys.argv
if len(getattr(sys, 'argv', [])) > 0:
p = os.path.dirname(os.path.dirname(pycompat.sysargv[0]))
if p != b'/':
path.extend(_rcfiles(os.path.join(p, root)))
path.extend(_rcfiles(b'/' + root))
return path
def userrcpath():
if pycompat.sysplatform == b'plan9':
return [encoding.environ[b'home'] + b'/lib/hgrc']
elif pycompat.isdarwin:
return [os.path.expanduser(b'~/.hgrc')]
else:
confighome = encoding.environ.get(b'XDG_CONFIG_HOME')
if confighome is None or not os.path.isabs(confighome):
confighome = os.path.expanduser(b'~/.config')
return [
os.path.expanduser(b'~/.hgrc'),
os.path.join(confighome, b'hg', b'hgrc'),
]
def termsize(ui):
try:
import termios
TIOCGWINSZ = termios.TIOCGWINSZ # unavailable on IRIX (issue3449)
except (AttributeError, ImportError):
return 80, 24
for dev in (ui.ferr, ui.fout, ui.fin):
try:
try:
fd = dev.fileno()
except AttributeError:
continue
if not os.isatty(fd):
continue
arri = fcntl.ioctl(fd, TIOCGWINSZ, b'\0' * 8)
height, width = array.array('h', arri)[:2]
if width > 0 and height > 0:
return width, height
except ValueError:
pass
except IOError as e:
if e[0] == errno.EINVAL: # pytype: disable=unsupported-operands
pass
else:
raise
return 80, 24