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
#require killdaemons
$ hg init test
$ cd test
$ echo a > a
$ hg ci -Ama
adding a
$ cd ..
$ hg clone test test2
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd test2
$ echo a >> a
$ hg ci -mb
Cloning with a password in the URL should not save the password in .hg/hgrc:
$ hg serve -p $HGPORT -d --pid-file=hg.pid -E errors.log
$ cat hg.pid >> $DAEMON_PIDS
$ hg clone http://foo:xyzzy@localhost:$HGPORT/ test3
requesting all changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 1 files
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cat test3/.hg/hgrc
# example repository config (see 'hg help config' for more info)
[paths]
default = http://foo@localhost:$HGPORT/
# path aliases to other clones of this repo in URLs or filesystem paths
# (see 'hg help config.paths' for more info)
#
# default:pushurl = ssh://jdoe@example.net/hg/jdoes-fork
# my-fork = ssh://jdoe@example.net/hg/jdoes-fork
# my-clone = /home/jdoe/jdoes-clone
[ui]
# name and email (local to this repository, optional), e.g.
# username = Jane Doe <jdoe@example.com>
$ killdaemons.py
expect error, cloning not allowed
$ echo '[web]' > .hg/hgrc
$ echo 'allowpull = false' >> .hg/hgrc
$ hg serve -p $HGPORT -d --pid-file=hg.pid -E errors.log
$ cat hg.pid >> $DAEMON_PIDS
$ hg clone http://localhost:$HGPORT/ test4 # bundle2+
requesting all changes
abort: authorization failed
[255]
$ hg clone http://localhost:$HGPORT/ test4 --config devel.legacy.exchange=bundle1
abort: authorization failed
[255]
$ killdaemons.py
serve errors
$ cat errors.log
$ req() {
> hg serve -p $HGPORT -d --pid-file=hg.pid -E errors.log
> cat hg.pid >> $DAEMON_PIDS
> hg --cwd ../test pull http://localhost:$HGPORT/
> killdaemons.py hg.pid
> echo % serve errors
> cat errors.log
> }
expect error, pulling not allowed
$ req
pulling from http://localhost:$HGPORT/
searching for changes
abort: authorization failed
% serve errors
$ cd ..