lock: block signal interrupt while making a lock file
On Windows where symlink isn't supported, util.makelock() could leave an empty
file if interrupted immediately after os.open(). This empty lock never dies
as it has no process id recorded.
ld = os.open(pathname, os.O_CREAT | os.O_WRONLY | os.O_EXCL)
# an interrupt may occur here
os.write(ld, info)
os.close(ld)
This was a long-standing bug of TortoiseHg which runs a command-server and
kills it by CTRL_C_EVENT, reported by random Windows users.
https://bitbucket.org/tortoisehg/thg/issues/4873/#comment-
43591129
At first, I tried to fix makelock() to clean up a stale lock file, which
turned out to be hard because any instructions may be interrupted by a
signal.
ld = None
try:
# CALL_FUNCTION # os.open(...)
# an interrupt may occur here
# STORE_FAST # ld = ...
ld = os.open(pathname, os.O_CREAT | os.O_WRONLY | os.O_EXCL)
os.write(ld, info)
...
return True
except:
if ld:
...
os.unlink(pathname)
return False
So I decided to block signals by temporarily replacing the signal handlers
so makelcok() and held = 1 will never be interrupted.
Many thanks to Fernando Najera for investigating the issue.
from __future__ import absolute_import, print_function
import os
import subprocess
import sys
if subprocess.call(['python', '%s/hghave' % os.environ['TESTDIR'],
'cacheable']):
sys.exit(80)
from mercurial import (
extensions,
hg,
localrepo,
pycompat,
ui as uimod,
util,
vfs as vfsmod,
)
if pycompat.ispy3:
xrange = range
class fakerepo(object):
def __init__(self):
self._filecache = {}
class fakevfs(object):
def join(self, p):
return p
vfs = fakevfs()
def unfiltered(self):
return self
def sjoin(self, p):
return p
@localrepo.repofilecache('x', 'y')
def cached(self):
print('creating')
return 'string from function'
def invalidate(self):
for k in self._filecache:
try:
delattr(self, k)
except AttributeError:
pass
def basic(repo):
print("* neither file exists")
# calls function
repo.cached
repo.invalidate()
print("* neither file still exists")
# uses cache
repo.cached
# create empty file
f = open('x', 'w')
f.close()
repo.invalidate()
print("* empty file x created")
# should recreate the object
repo.cached
f = open('x', 'w')
f.write('a')
f.close()
repo.invalidate()
print("* file x changed size")
# should recreate the object
repo.cached
repo.invalidate()
print("* nothing changed with either file")
# stats file again, reuses object
repo.cached
# atomic replace file, size doesn't change
# hopefully st_mtime doesn't change as well so this doesn't use the cache
# because of inode change
f = vfsmod.vfs('.')('x', 'w', atomictemp=True)
f.write('b')
f.close()
repo.invalidate()
print("* file x changed inode")
repo.cached
# create empty file y
f = open('y', 'w')
f.close()
repo.invalidate()
print("* empty file y created")
# should recreate the object
repo.cached
f = open('y', 'w')
f.write('A')
f.close()
repo.invalidate()
print("* file y changed size")
# should recreate the object
repo.cached
f = vfsmod.vfs('.')('y', 'w', atomictemp=True)
f.write('B')
f.close()
repo.invalidate()
print("* file y changed inode")
repo.cached
f = vfsmod.vfs('.')('x', 'w', atomictemp=True)
f.write('c')
f.close()
f = vfsmod.vfs('.')('y', 'w', atomictemp=True)
f.write('C')
f.close()
repo.invalidate()
print("* both files changed inode")
repo.cached
def fakeuncacheable():
def wrapcacheable(orig, *args, **kwargs):
return False
def wrapinit(orig, *args, **kwargs):
pass
originit = extensions.wrapfunction(util.cachestat, '__init__', wrapinit)
origcacheable = extensions.wrapfunction(util.cachestat, 'cacheable',
wrapcacheable)
for fn in ['x', 'y']:
try:
os.remove(fn)
except OSError:
pass
basic(fakerepo())
util.cachestat.cacheable = origcacheable
util.cachestat.__init__ = originit
def test_filecache_synced():
# test old behavior that caused filecached properties to go out of sync
os.system('hg init && echo a >> a && hg ci -qAm.')
repo = hg.repository(uimod.ui.load())
# first rollback clears the filecache, but changelog to stays in __dict__
repo.rollback()
repo.commit('.')
# second rollback comes along and touches the changelog externally
# (file is moved)
repo.rollback()
# but since changelog isn't under the filecache control anymore, we don't
# see that it changed, and return the old changelog without reconstructing
# it
repo.commit('.')
def setbeforeget(repo):
os.remove('x')
os.remove('y')
repo.cached = 'string set externally'
repo.invalidate()
print("* neither file exists")
print(repo.cached)
repo.invalidate()
f = open('x', 'w')
f.write('a')
f.close()
print("* file x created")
print(repo.cached)
repo.cached = 'string 2 set externally'
repo.invalidate()
print("* string set externally again")
print(repo.cached)
repo.invalidate()
f = open('y', 'w')
f.write('b')
f.close()
print("* file y created")
print(repo.cached)
def antiambiguity():
filename = 'ambigcheck'
# try some times, because reproduction of ambiguity depends on
# "filesystem time"
for i in xrange(5):
fp = open(filename, 'w')
fp.write('FOO')
fp.close()
oldstat = os.stat(filename)
if oldstat.st_ctime != oldstat.st_mtime:
# subsequent changing never causes ambiguity
continue
repetition = 3
# repeat changing via checkambigatclosing, to examine whether
# st_mtime is advanced multiple times as expected
for i in xrange(repetition):
# explicit closing
fp = vfsmod.checkambigatclosing(open(filename, 'a'))
fp.write('FOO')
fp.close()
# implicit closing by "with" statement
with vfsmod.checkambigatclosing(open(filename, 'a')) as fp:
fp.write('BAR')
newstat = os.stat(filename)
if oldstat.st_ctime != newstat.st_ctime:
# timestamp ambiguity was naturally avoided while repetition
continue
# st_mtime should be advanced "repetition * 2" times, because
# all changes occurred at same time (in sec)
expected = (oldstat.st_mtime + repetition * 2) & 0x7fffffff
if newstat.st_mtime != expected:
print("'newstat.st_mtime %s is not %s (as %s + %s * 2)" %
(newstat.st_mtime, expected, oldstat.st_mtime, repetition))
# no more examination is needed regardless of result
break
else:
# This platform seems too slow to examine anti-ambiguity
# of file timestamp (or test happened to be executed at
# bad timing). Exit silently in this case, because running
# on other faster platforms can detect problems
pass
print('basic:')
print()
basic(fakerepo())
print()
print('fakeuncacheable:')
print()
fakeuncacheable()
test_filecache_synced()
print()
print('setbeforeget:')
print()
setbeforeget(fakerepo())
print()
print('antiambiguity:')
print()
antiambiguity()