lock: while releasing, unlink lockfile even if the release function throws
Consider a hypothetical bug in the release function that causes it to raise an
exception. Also consider the bisect command, which saves its state in a finally
clause. Saving the state requires acquiring the wlock.
If we don't unlink the lockfile when the exception is thrown, we'll try to
acquire the wlock again. We're going to try and acquire a lock again while our
old lockfile is on disk. The PID on disk is our own, and of course we're still
running, so we won't take over the lock. Hence we'll be stuck waiting for a
lock that we left behind ourselves.
To avoid this, always unlink the lockfile. This preserves the invariant that
self.held > 0 is equivalent to the lockfile existing on disk.
#!/usr/bin/env python
from mercurial import demandimport
demandimport.enable()
import sys
from mercurial.i18n import _
from mercurial import simplemerge, fancyopts, util, ui
options = [('L', 'label', [], _('labels to use on conflict markers')),
('a', 'text', None, _('treat all files as text')),
('p', 'print', None,
_('print results instead of overwriting LOCAL')),
('', 'no-minimal', None, _('no effect (DEPRECATED)')),
('h', 'help', None, _('display help and exit')),
('q', 'quiet', None, _('suppress output'))]
usage = _('''simplemerge [OPTS] LOCAL BASE OTHER
Simple three-way file merge utility with a minimal feature set.
Apply to LOCAL the changes necessary to go from BASE to OTHER.
By default, LOCAL is overwritten with the results of this operation.
''')
class ParseError(Exception):
"""Exception raised on errors in parsing the command line."""
def showhelp():
sys.stdout.write(usage)
sys.stdout.write('\noptions:\n')
out_opts = []
for shortopt, longopt, default, desc in options:
out_opts.append(('%2s%s' % (shortopt and '-%s' % shortopt,
longopt and ' --%s' % longopt),
'%s' % desc))
opts_len = max([len(opt[0]) for opt in out_opts])
for first, second in out_opts:
sys.stdout.write(' %-*s %s\n' % (opts_len, first, second))
try:
for fp in (sys.stdin, sys.stdout, sys.stderr):
util.setbinary(fp)
opts = {}
try:
args = fancyopts.fancyopts(sys.argv[1:], options, opts)
except fancyopts.getopt.GetoptError, e:
raise ParseError(e)
if opts['help']:
showhelp()
sys.exit(0)
if len(args) != 3:
raise ParseError(_('wrong number of arguments'))
sys.exit(simplemerge.simplemerge(ui.ui(), *args, **opts))
except ParseError, e:
sys.stdout.write("%s: %s\n" % (sys.argv[0], e))
showhelp()
sys.exit(1)
except util.Abort, e:
sys.stderr.write("abort: %s\n" % e)
sys.exit(255)
except KeyboardInterrupt:
sys.exit(255)