worker: rewrite error handling so os._exit covers all cases
Previously the worker error handling is like:
pid = os.fork() --+
if pid == 0: |
.... | problematic
.... --+
try: --+
.... | worker error handling
--+
If a signal arrives when Python is executing the "problematic" lines, an
external error handling (dispatch.py) will take over the control flow and
it's no longer guaranteed "os._exit" is called (see
86cd09bc13ba for why it
is necessary).
This patch rewrites the error handling so it covers all possible code paths
for a worker even during fork.
Note: "os.getpid() == parentpid" is used to test if the process is parent or
not intentionally, instead of checking "pid", because "pid = os.fork()" may
be not atomic - it's possible that that a signal hits the worker before the
assignment completes [1]. The newly added test replaces "os.fork" to
exercise that extreme case.
[1]: CPython compiles "pid = os.fork()" to 2 byte codes: "CALL_FUNCTION" and
"STORE_FAST", so it's probably not atomic:
def f():
pid = os.fork()
dis.dis(f)
2 0 LOAD_GLOBAL 0 (os)
3 LOAD_ATTR 1 (fork)
6 CALL_FUNCTION 0
9 STORE_FAST 0 (pid)
12 LOAD_CONST 0 (None)
15 RETURN_VALUE
#!/usr/bin/env python
#
# check-perf-code - (historical) portability checker for contrib/perf.py
from __future__ import absolute_import
import os
import sys
# write static check patterns here
perfpypats = [
[
(r'(branchmap|repoview)\.subsettable',
"use getbranchmapsubsettable() for early Mercurial"),
(r'\.(vfs|svfs|opener|sopener)',
"use getvfs()/getsvfs() for early Mercurial"),
(r'ui\.configint',
"use getint() instead of ui.configint() for early Mercurial"),
],
# warnings
[
]
]
def modulewhitelist(names):
replacement = [('.py', ''), ('.c', ''), # trim suffix
('mercurial%s' % (os.sep), ''), # trim "mercurial/" path
]
ignored = set(['__init__'])
modules = {}
# convert from file name to module name, and count # of appearances
for name in names:
name = name.strip()
for old, new in replacement:
name = name.replace(old, new)
if name not in ignored:
modules[name] = modules.get(name, 0) + 1
# list up module names, which appear multiple times
whitelist = []
for name, count in modules.items():
if count > 1:
whitelist.append(name)
return whitelist
if __name__ == "__main__":
# in this case, it is assumed that result of "hg files" at
# multiple revisions is given via stdin
whitelist = modulewhitelist(sys.stdin)
assert whitelist, "module whitelist is empty"
# build up module whitelist check from file names given at runtime
perfpypats[0].append(
# this matching pattern assumes importing modules from
# "mercurial" package in the current style below, for simplicity
#
# from mercurial import (
# foo,
# bar,
# baz
# )
((r'from mercurial import [(][a-z0-9, \n#]*\n(?! *%s,|^[ #]*\n|[)])'
% ',| *'.join(whitelist)),
"import newer module separately in try clause for early Mercurial"
))
# import contrib/check-code.py as checkcode
assert 'RUNTESTDIR' in os.environ, "use check-perf-code.py in *.t script"
contribpath = os.path.join(os.environ['RUNTESTDIR'], '..', 'contrib')
sys.path.insert(0, contribpath)
checkcode = __import__('check-code')
# register perf.py specific entry with "checks" in check-code.py
checkcode.checks.append(('perf.py', r'contrib/perf.py$', '',
checkcode.pyfilters, perfpypats))
sys.exit(checkcode.main())