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
$ hg init
Revision 0:
$ echo "unchanged" > unchanged
$ echo "remove me" > remove
$ echo "copy me" > copy
$ echo "move me" > move
$ for i in 1 2 3 4 5 6 7 8 9; do
> echo "merge ok $i" >> zzz1_merge_ok
> done
$ echo "merge bad" > zzz2_merge_bad
$ hg ci -Am "revision 0"
adding copy
adding move
adding remove
adding unchanged
adding zzz1_merge_ok
adding zzz2_merge_bad
Revision 1:
$ hg rm remove
$ hg mv move moved
$ hg cp copy copied
$ echo "added" > added
$ hg add added
$ echo "new first line" > zzz1_merge_ok
$ hg cat zzz1_merge_ok >> zzz1_merge_ok
$ echo "new last line" >> zzz2_merge_bad
$ hg ci -m "revision 1"
Local changes to revision 0:
$ hg co 0
4 files updated, 0 files merged, 3 files removed, 0 files unresolved
$ echo "new last line" >> zzz1_merge_ok
$ echo "another last line" >> zzz2_merge_bad
$ hg diff --nodates | grep "^[+-][^<>]"
--- a/zzz1_merge_ok
+++ b/zzz1_merge_ok
+new last line
--- a/zzz2_merge_bad
+++ b/zzz2_merge_bad
+another last line
$ hg st
M zzz1_merge_ok
M zzz2_merge_bad
Local merge with bad merge tool:
$ HGMERGE=false hg co
merging zzz1_merge_ok
merging zzz2_merge_bad
merging zzz2_merge_bad failed!
3 files updated, 1 files merged, 2 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges
[1]
$ hg co 0
merging zzz1_merge_ok
merging zzz2_merge_bad
warning: conflicts while merging zzz2_merge_bad! (edit, then use 'hg resolve --mark')
2 files updated, 1 files merged, 3 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges
[1]
$ hg diff --nodates | grep "^[+-][^<>]"
--- a/zzz1_merge_ok
+++ b/zzz1_merge_ok
+new last line
--- a/zzz2_merge_bad
+++ b/zzz2_merge_bad
+another last line
+=======
$ hg st
M zzz1_merge_ok
M zzz2_merge_bad
? zzz2_merge_bad.orig
Local merge with conflicts:
$ hg co
merging zzz1_merge_ok
merging zzz2_merge_bad
warning: conflicts while merging zzz2_merge_bad! (edit, then use 'hg resolve --mark')
3 files updated, 1 files merged, 2 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges
[1]
$ hg co 0 --config 'ui.origbackuppath=.hg/origbackups'
merging zzz1_merge_ok
merging zzz2_merge_bad
warning: conflicts while merging zzz2_merge_bad! (edit, then use 'hg resolve --mark')
2 files updated, 1 files merged, 3 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges
[1]
Are orig files from the last commit where we want them?
$ ls .hg/origbackups
zzz2_merge_bad.orig
$ hg diff --nodates | grep "^[+-][^<>]"
--- a/zzz1_merge_ok
+++ b/zzz1_merge_ok
+new last line
--- a/zzz2_merge_bad
+++ b/zzz2_merge_bad
+another last line
+=======
+=======
+new last line
+=======
$ hg st
M zzz1_merge_ok
M zzz2_merge_bad
? zzz2_merge_bad.orig
Local merge without conflicts:
$ hg revert zzz2_merge_bad
$ hg co
merging zzz1_merge_ok
4 files updated, 1 files merged, 2 files removed, 0 files unresolved
$ hg diff --nodates | grep "^[+-][^<>]"
--- a/zzz1_merge_ok
+++ b/zzz1_merge_ok
+new last line
$ hg st
M zzz1_merge_ok
? zzz2_merge_bad.orig