commands: make commit acquire locks before processing (issue4368)
Before this patch, "hg commit" (process A) executes steps below:
1. get current branch heads via 'repo.branchheads()'
- cache 'repo.changelog'
2. invoke 'repo.commit()'
3. acquire wlock
- invalidate 'repo.dirstate'
4. access 'repo.dirstate'
- re-read '.hg/dirstate'
- check validity of parent revisions with 'repo.changelog'
5. invoke 'repo.commitctx()'
6. acquire store lock (slock)
- invalidate 'repo.changelog'
7. do committing
8. release slock
9. release wlock
10. check new branch head (via 'cmdutil.commitstatus()')
If acquisition of wlock at (3) above waits for another "hg commit"
(process B) or so running parallelly to release wlock, process A
causes creating orphan revision, because:
- '.hg/dirstate' refers the revision, which is newly added by
process B, as its parent
- but already cached 'repo.changelog' doesn't contain such revision
- therefore, validating parents of '.hg/dirstate' at (4) above
replaces such revision with 'nullid'
Then, process A creates "orphan" revision, of which parent is "null"
revision.
In addition to it, "created new head" may be shown at the end of
process A unintentionally, if store is updated parallelly, because
both getting branch heads (1) and checking new branch head (10) are
executed outside slock scope.
To avoid this issue, this patch makes "hg commit" acquire wlock and
slock before processing.
This patch resolves the issue between "hg commit" processes, but not
one between "hg commit" and other commands. Subsequent patches resolve
the latter.
Even after this patch, there are still corner case problems below:
- filecache may overlook changes of '.hg/dirstate', and it causes
similar issue (see below for detail)
https://bz.mercurial-scm.org/show_bug.cgi?id=4368#c10
- 3rd party extension may cause similar issue, if it directly uses
'repo.commit()' without acquisition of wlock and slock
This can be fixed by acquisition of slock at the beginning of
'repo.commit()', but it seems suitable for "default" branch
In fact, acquisition of slock itself is already introduced at
"default" branch by 4414d500604f, but acquisition is not at the
beginning of 'repo.commit()'.
This patch also changes some tests:
- test-fncache.t needs this tricky wrapping, to release (= forced
failure of) wlock certainly
- order of "hg commit" output is changed by widening scope of locks,
because some hooks are fired after releasing wlock
#require killdaemons
$ hgserve() {
> hg serve -a localhost -p $HGPORT1 -d --pid-file=hg.pid \
> -E errors.log -v $@ > startup.log
> # Grepping hg serve stdout would hang on Windows
> grep -v 'listening at' startup.log
> cat hg.pid >> "$DAEMON_PIDS"
> }
$ hg init a
$ hg --encoding utf-8 -R a branch æ
marked working directory as branch \xc3\xa6 (esc)
(branches are permanent and global, did you want a bookmark?)
$ echo foo > a/foo
$ hg -R a ci -Am foo
adding foo
$ hgserve -R a --config web.push_ssl=False --config web.allow_push=* --encoding latin1
$ hg --encoding utf-8 clone http://localhost:$HGPORT1 b
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
updating to branch \xc3\xa6 (esc)
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg --encoding utf-8 -R b log
changeset: 0:867c11ce77b8
branch: \xc3\xa6 (esc)
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: foo
$ echo bar >> b/foo
$ hg -R b ci -m bar
$ hg --encoding utf-8 -R b push
pushing to http://localhost:$HGPORT1/
searching for changes
remote: adding changesets
remote: adding manifests
remote: adding file changes
remote: added 1 changesets with 1 changes to 1 files
$ hg -R a --encoding utf-8 log
changeset: 1:58e7c90d67cb
branch: \xc3\xa6 (esc)
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: bar
changeset: 0:867c11ce77b8
branch: \xc3\xa6 (esc)
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: foo
$ killdaemons.py hg.pid
verify 7e7d56fe4833 (encoding fallback in branchmap to maintain compatibility with 1.3.x)
$ cat <<EOF > oldhg
> import sys
> from mercurial import ui, hg, commands
>
> class StdoutWrapper(object):
> def __init__(self, stdout):
> self._file = stdout
>
> def write(self, data):
> if data == '47\n':
> # latin1 encoding is one %xx (3 bytes) shorter
> data = '44\n'
> elif data.startswith('%C3%A6 '):
> # translate to latin1 encoding
> data = '%%E6 %s' % data[7:]
> self._file.write(data)
>
> def __getattr__(self, name):
> return getattr(self._file, name)
>
> sys.stdout = StdoutWrapper(sys.stdout)
> sys.stderr = StdoutWrapper(sys.stderr)
>
> myui = ui.ui()
> repo = hg.repository(myui, 'a')
> commands.serve(myui, repo, stdio=True, cmdserver=False)
> EOF
$ echo baz >> b/foo
$ hg -R b ci -m baz
$ hg push -R b -e 'python oldhg' ssh://dummy/ --encoding latin1
pushing to ssh://dummy/
searching for changes
remote: adding changesets
remote: adding manifests
remote: adding file changes
remote: added 1 changesets with 1 changes to 1 files