contrib/lock-checker.py

tests: fix toctou race in tinyproxy.py (issue3795)

test-http-proxy.t sometimes failed with:
    File ".../tests/tinyproxy.py", line 110, in _read_write
      data = i.recv(8192)
  error: (104, 'Connection reset by peer')

This might have started showing up with a9fd11ffa13f ... but it has apparently
also been seen before. I don't see anything in a9fd11ffa13f that can explain
it. It seems to be a race in test, in the tinyproxy helper:

Tinyproxy found an incoming socket using select(). It would break the loop if
an error had been detected on the socket, but there was no error and it tried
to recv() from the socket. That failed - apparently because it had been reset
after select().

Errors in the recv() will now be caught and will break the loop like errors
detected by select() would.

(send() could also fail in a similar way ... but using the same solution there
and losing data we have read doesn't feel right.)

"""Extension to verify locks are obtained in the required places.

This works by wrapping functions that should be surrounded by a lock
and asserting the lock is held. Missing locks are called out with a
traceback printed to stderr.

This currently only checks store locks, not working copy locks.
"""
import os
import traceback

def _warnstack(ui, msg, skip=1):
    '''issue warning with the message and the current stack, skipping the
    skip last entries'''
    ui.warn('%s at:\n' % msg)
    entries = traceback.extract_stack()[:-skip]
    fnmax = max(len(entry[0]) for entry in entries)
    for fn, ln, func, _text in entries:
        ui.warn(' %*s:%-4s in %s\n' % (fnmax, fn, ln, func))

def _checklock(repo):
    l = repo._lockref and repo._lockref()
    if l is None or not l.held:
        _warnstack(repo.ui, 'missing lock', skip=2)

def reposetup(ui, repo):
    orig = repo.__class__
    class lockcheckrepo(repo.__class__):
        def _writejournal(self, *args, **kwargs):
            _checklock(self)
            return orig._writejournal(self, *args, **kwargs)

        def transaction(self, *args, **kwargs):
            _checklock(self)
            return orig.transaction(self, *args, **kwargs)

        # TODO(durin42): kiilerix had a commented-out lock check in
        # _writebranchcache and _writerequirements

        def _tag(self, *args, **kwargs):
            _checklock(self)
            return orig._tag(self, *args, **kwargs)

        def write(self, *args, **kwargs):
            assert os.path.lexists(self._join('.hg/wlock'))
            return orig.write(self, *args, **kwargs)

    repo.__class__ = lockcheckrepo