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
from mercurial import (
dispatch,
)
def testdispatch(cmd):
"""Simple wrapper around dispatch.dispatch()
Prints command and result value, but does not handle quoting.
"""
print(b"running: %s" % (cmd,))
req = dispatch.request(cmd.split())
result = dispatch.dispatch(req)
print(b"result: %r" % (result,))
testdispatch(b"init test1")
os.chdir('test1')
# create file 'foo', add and commit
f = open('foo', 'wb')
f.write(b'foo\n')
f.close()
testdispatch(b"add foo")
testdispatch(b"commit -m commit1 -d 2000-01-01 foo")
# append to file 'foo' and commit
f = open('foo', 'ab')
f.write(b'bar\n')
f.close()
testdispatch(b"commit -m commit2 -d 2000-01-02 foo")
# check 88803a69b24 (fancyopts modified command table)
testdispatch(b"log -r 0")
testdispatch(b"log -r tip")