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
# destutil.py - Mercurial utility function for command destination
#
# Copyright Matt Mackall <mpm@selenic.com> and other
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from __future__ import absolute_import
from .i18n import _
from . import (
bookmarks,
error,
obsolete,
scmutil,
)
def _destupdateobs(repo, clean):
"""decide of an update destination from obsolescence markers"""
node = None
wc = repo[None]
p1 = wc.p1()
movemark = None
if p1.obsolete() and not p1.children():
# allow updating to successors
successors = obsolete.successorssets(repo, p1.node())
# behavior of certain cases is as follows,
#
# divergent changesets: update to highest rev, similar to what
# is currently done when there are more than one head
# (i.e. 'tip')
#
# replaced changesets: same as divergent except we know there
# is no conflict
#
# pruned changeset: no update is done; though, we could
# consider updating to the first non-obsolete parent,
# similar to what is current done for 'hg prune'
if successors:
# flatten the list here handles both divergent (len > 1)
# and the usual case (len = 1)
successors = [n for sub in successors for n in sub]
# get the max revision for the given successors set,
# i.e. the 'tip' of a set
node = repo.revs('max(%ln)', successors).first()
if bookmarks.isactivewdirparent(repo):
movemark = repo['.'].node()
return node, movemark, None
def _destupdatebook(repo, clean):
"""decide on an update destination from active bookmark"""
# we also move the active bookmark, if any
activemark = None
node, movemark = bookmarks.calculateupdate(repo.ui, repo, None)
if node is not None:
activemark = node
return node, movemark, activemark
def _destupdatebranch(repo, clean):
"""decide on an update destination from current branch
This ignores closed branch heads.
"""
wc = repo[None]
movemark = node = None
currentbranch = wc.branch()
if clean:
currentbranch = repo['.'].branch()
if currentbranch in repo.branchmap():
heads = repo.branchheads(currentbranch)
if heads:
node = repo.revs('max(.::(%ln))', heads).first()
if bookmarks.isactivewdirparent(repo):
movemark = repo['.'].node()
elif currentbranch == 'default' and not wc.p1():
# "null" parent belongs to "default" branch, but it doesn't exist, so
# update to the tipmost non-closed branch head
node = repo.revs('max(head() and not closed())').first()
else:
node = repo['.'].node()
return node, movemark, None
def _destupdatebranchfallback(repo, clean):
"""decide on an update destination from closed heads in current branch"""
wc = repo[None]
currentbranch = wc.branch()
movemark = None
if currentbranch in repo.branchmap():
# here, all descendant branch heads are closed
heads = repo.branchheads(currentbranch, closed=True)
assert heads, "any branch has at least one head"
node = repo.revs('max(.::(%ln))', heads).first()
assert node is not None, ("any revision has at least "
"one descendant branch head")
if bookmarks.isactivewdirparent(repo):
movemark = repo['.'].node()
else:
# here, no "default" branch, and all branches are closed
node = repo.lookup('tip')
assert node is not None, "'tip' exists even in empty repository"
return node, movemark, None
# order in which each step should be evaluated
# steps are run until one finds a destination
destupdatesteps = ['evolution', 'bookmark', 'branch', 'branchfallback']
# mapping to ease extension overriding steps.
destupdatestepmap = {'evolution': _destupdateobs,
'bookmark': _destupdatebook,
'branch': _destupdatebranch,
'branchfallback': _destupdatebranchfallback,
}
def destupdate(repo, clean=False):
"""destination for bare update operation
return (rev, movemark, activemark)
- rev: the revision to update to,
- movemark: node to move the active bookmark from
(cf bookmark.calculate update),
- activemark: a bookmark to activate at the end of the update.
"""
node = movemark = activemark = None
for step in destupdatesteps:
node, movemark, activemark = destupdatestepmap[step](repo, clean)
if node is not None:
break
rev = repo[node].rev()
return rev, movemark, activemark
msgdestmerge = {
# too many matching divergent bookmark
'toomanybookmarks':
{'merge':
(_("multiple matching bookmarks to merge -"
" please merge with an explicit rev or bookmark"),
_("run 'hg heads' to see all heads")),
'rebase':
(_("multiple matching bookmarks to rebase -"
" please rebase to an explicit rev or bookmark"),
_("run 'hg heads' to see all heads")),
},
# no other matching divergent bookmark
'nootherbookmarks':
{'merge':
(_("no matching bookmark to merge - "
"please merge with an explicit rev or bookmark"),
_("run 'hg heads' to see all heads")),
'rebase':
(_("no matching bookmark to rebase - "
"please rebase to an explicit rev or bookmark"),
_("run 'hg heads' to see all heads")),
},
# branch have too many unbookmarked heads, no obvious destination
'toomanyheads':
{'merge':
(_("branch '%s' has %d heads - please merge with an explicit rev"),
_("run 'hg heads .' to see heads")),
'rebase':
(_("branch '%s' has %d heads - please rebase to an explicit rev"),
_("run 'hg heads .' to see heads")),
},
# branch have no other unbookmarked heads
'bookmarkedheads':
{'merge':
(_("heads are bookmarked - please merge with an explicit rev"),
_("run 'hg heads' to see all heads")),
'rebase':
(_("heads are bookmarked - please rebase to an explicit rev"),
_("run 'hg heads' to see all heads")),
},
# branch have just a single heads, but there is other branches
'nootherbranchheads':
{'merge':
(_("branch '%s' has one head - please merge with an explicit rev"),
_("run 'hg heads' to see all heads")),
'rebase':
(_("branch '%s' has one head - please rebase to an explicit rev"),
_("run 'hg heads' to see all heads")),
},
# repository have a single head
'nootherheads':
{'merge':
(_('nothing to merge'),
None),
'rebase':
(_('nothing to rebase'),
None),
},
# repository have a single head and we are not on it
'nootherheadsbehind':
{'merge':
(_('nothing to merge'),
_("use 'hg update' instead")),
'rebase':
(_('nothing to rebase'),
_("use 'hg update' instead")),
},
# We are not on a head
'notatheads':
{'merge':
(_('working directory not at a head revision'),
_("use 'hg update' or merge with an explicit revision")),
'rebase':
(_('working directory not at a head revision'),
_("use 'hg update' or rebase to an explicit revision"))
},
'emptysourceset':
{'merge':
(_('source set is empty'),
None),
'rebase':
(_('source set is empty'),
None),
},
'multiplebranchessourceset':
{'merge':
(_('source set is rooted in multiple branches'),
None),
'rebase':
(_('rebaseset is rooted in multiple named branches'),
_('specify an explicit destination with --dest')),
},
}
def _destmergebook(repo, action='merge', sourceset=None, destspace=None):
"""find merge destination in the active bookmark case"""
node = None
bmheads = repo.bookmarkheads(repo._activebookmark)
curhead = repo[repo._activebookmark].node()
if len(bmheads) == 2:
if curhead == bmheads[0]:
node = bmheads[1]
else:
node = bmheads[0]
elif len(bmheads) > 2:
msg, hint = msgdestmerge['toomanybookmarks'][action]
raise error.ManyMergeDestAbort(msg, hint=hint)
elif len(bmheads) <= 1:
msg, hint = msgdestmerge['nootherbookmarks'][action]
raise error.NoMergeDestAbort(msg, hint=hint)
assert node is not None
return node
def _destmergebranch(repo, action='merge', sourceset=None, onheadcheck=True,
destspace=None):
"""find merge destination based on branch heads"""
node = None
if sourceset is None:
sourceset = [repo[repo.dirstate.p1()].rev()]
branch = repo.dirstate.branch()
elif not sourceset:
msg, hint = msgdestmerge['emptysourceset'][action]
raise error.NoMergeDestAbort(msg, hint=hint)
else:
branch = None
for ctx in repo.set('roots(%ld::%ld)', sourceset, sourceset):
if branch is not None and ctx.branch() != branch:
msg, hint = msgdestmerge['multiplebranchessourceset'][action]
raise error.ManyMergeDestAbort(msg, hint=hint)
branch = ctx.branch()
bheads = repo.branchheads(branch)
onhead = repo.revs('%ld and %ln', sourceset, bheads)
if onheadcheck and not onhead:
# Case A: working copy if not on a head. (merge only)
#
# This is probably a user mistake We bailout pointing at 'hg update'
if len(repo.heads()) <= 1:
msg, hint = msgdestmerge['nootherheadsbehind'][action]
else:
msg, hint = msgdestmerge['notatheads'][action]
raise error.Abort(msg, hint=hint)
# remove heads descendants of source from the set
bheads = list(repo.revs('%ln - (%ld::)', bheads, sourceset))
# filters out bookmarked heads
nbhs = list(repo.revs('%ld - bookmark()', bheads))
if destspace is not None:
# restrict search space
# used in the 'hg pull --rebase' case, see issue 5214.
nbhs = list(repo.revs('%ld and %ld', destspace, nbhs))
if len(nbhs) > 1:
# Case B: There is more than 1 other anonymous heads
#
# This means that there will be more than 1 candidate. This is
# ambiguous. We abort asking the user to pick as explicit destination
# instead.
msg, hint = msgdestmerge['toomanyheads'][action]
msg %= (branch, len(bheads) + 1)
raise error.ManyMergeDestAbort(msg, hint=hint)
elif not nbhs:
# Case B: There is no other anonymous heads
#
# This means that there is no natural candidate to merge with.
# We abort, with various messages for various cases.
if bheads:
msg, hint = msgdestmerge['bookmarkedheads'][action]
elif len(repo.heads()) > 1:
msg, hint = msgdestmerge['nootherbranchheads'][action]
msg %= branch
elif not onhead:
# if 'onheadcheck == False' (rebase case),
# this was not caught in Case A.
msg, hint = msgdestmerge['nootherheadsbehind'][action]
else:
msg, hint = msgdestmerge['nootherheads'][action]
raise error.NoMergeDestAbort(msg, hint=hint)
else:
node = nbhs[0]
assert node is not None
return node
def destmerge(repo, action='merge', sourceset=None, onheadcheck=True,
destspace=None):
"""return the default destination for a merge
(or raise exception about why it can't pick one)
:action: the action being performed, controls emitted error message
"""
# destspace is here to work around issues with `hg pull --rebase` see
# issue5214 for details
if repo._activebookmark:
node = _destmergebook(repo, action=action, sourceset=sourceset,
destspace=destspace)
else:
node = _destmergebranch(repo, action=action, sourceset=sourceset,
onheadcheck=onheadcheck, destspace=destspace)
return repo[node].rev()
histeditdefaultrevset = 'reverse(only(.) and not public() and not ::merge())'
def desthistedit(ui, repo):
"""Default base revision to edit for `hg histedit`."""
default = ui.config('histedit', 'defaultrev', histeditdefaultrevset)
if default:
revs = scmutil.revrange(repo, [default])
if revs:
# The revset supplied by the user may not be in ascending order nor
# take the first revision. So do this manually.
revs.sort()
return revs.first()
return None
def _statusotherbook(ui, repo):
bmheads = repo.bookmarkheads(repo._activebookmark)
curhead = repo[repo._activebookmark].node()
if repo.revs('%n and parents()', curhead):
# we are on the active bookmark
bmheads = [b for b in bmheads if curhead != b]
if bmheads:
msg = _('%i other divergent bookmarks for "%s"\n')
ui.status(msg % (len(bmheads), repo._activebookmark))
def _statusotherbranchheads(ui, repo):
currentbranch = repo.dirstate.branch()
allheads = repo.branchheads(currentbranch, closed=True)
heads = repo.branchheads(currentbranch)
if repo.revs('%ln and parents()', allheads):
# we are on a head, even though it might be closed
#
# on closed otherheads
# ========= ==========
# o 0 all heads for current branch are closed
# N only descendant branch heads are closed
# x 0 there is only one non-closed branch head
# N there are some non-closed branch heads
# ========= ==========
otherheads = repo.revs('%ln - parents()', heads)
if repo['.'].closesbranch():
ui.warn(_('no open descendant heads on branch "%s", '
'updating to a closed head\n') %
(currentbranch))
if otherheads:
ui.warn(_("(committing will reopen the head, "
"use 'hg heads .' to see %i other heads)\n") %
(len(otherheads)))
else:
ui.warn(_('(committing will reopen branch "%s")\n') %
(currentbranch))
elif otherheads:
ui.status(_('%i other heads for branch "%s"\n') %
(len(otherheads), currentbranch))
def statusotherdests(ui, repo):
"""Print message about other head"""
# XXX we should probably include a hint:
# - about what to do
# - how to see such heads
if repo._activebookmark:
_statusotherbook(ui, repo)
else:
_statusotherbranchheads(ui, repo)