Mercurial > hg
view tests/test-paths.t @ 43709:039fbd14d4e2
lock: fix race in lock-breaking code
With low frequency, I see hg pulls fail with output like:
abort: no such file or directory: .hg/store/lock
I think what happens is, in lock.py, in:
def _testlock(self, locker):
if not self._lockshouldbebroken(locker):
return locker
# if locker dead, break lock. must do this with another lock
# held, or can race and break valid lock.
try:
with lock(self.vfs, self.f + b'.break', timeout=0):
self.vfs.unlink(self.f)
except error.LockError:
return locker
if a lock is breakable on disk, and two hg processes concurrently get
to the "if locker dead" comment, a possible interleaving is: process1
finishes executing the function and then process2 finishes executing
the function. If that happens, process2 will either get ENOENT in
self.vfs.unlink (resulting in the spurious failure above), or break a
valid lock and potentially cause repository corruption.
The fix is simple enough: make sure the lock is breakable _inside_ the
critical section, because only then can we know that no other process
can invalidate our knowledge on the lock on disk.
I don't think there are tests for this. I've tested this manually
with:
diff --git a/mercurial/lock.py b/mercurial/lock.py
--- a/mercurial/lock.py
+++ b/mercurial/lock.py
@@ -351,6 +351,8 @@ class lock(object):
if not self._lockshouldbebroken(locker):
return locker
+ import random
+ time.sleep(1. + random.random())
# if locker dead, break lock. must do this with another lock
# held, or can race and break valid lock.
try:
@@ -358,6 +360,7 @@ class lock(object):
self.vfs.unlink(self.f)
except error.LockError:
return locker
+ time.sleep(1)
def testlock(self):
"""return id of locker if lock is valid, else None.
and I see this change of behavior before/after this commit:
$ $hg init repo
$ cd repo
$ ln -s $HOSTNAME/effffffc:987654321 .hg/wlock
$ touch a
$ $hg commit -Am_ & $hg commit -Am _; wait
-abort: No such file or directory: '/tmp/repo/.hg/wlock'
adding a
+warning: ignoring unknown working parent 679a8959a8ca!
+nothing changed
Differential Revision: https://phab.mercurial-scm.org/D7199
author | Valentin Gatien-Baron <valentin.gatienbaron@gmail.com> |
---|---|
date | Mon, 18 Nov 2019 20:10:38 -0800 |
parents | 4441705b7111 |
children | 83b0a5c0dfec |
line wrap: on
line source
$ hg init a $ hg clone a b updating to branch default 0 files updated, 0 files merged, 0 files removed, 0 files unresolved $ cd a with no paths: $ hg paths $ hg paths unknown not found! [1] $ hg paths -Tjson [ ] with paths: $ echo '[paths]' >> .hg/hgrc $ echo 'dupe = ../b#tip' >> .hg/hgrc $ echo 'expand = $SOMETHING/bar' >> .hg/hgrc $ hg in dupe comparing with $TESTTMP/b no changes found [1] $ cd .. $ hg -R a in dupe comparing with $TESTTMP/b no changes found [1] $ cd a $ hg paths dupe = $TESTTMP/b#tip expand = $TESTTMP/a/$SOMETHING/bar $ SOMETHING=foo hg paths dupe = $TESTTMP/b#tip expand = $TESTTMP/a/foo/bar #if msys $ SOMETHING=//foo hg paths dupe = $TESTTMP/b#tip expand = /foo/bar #else $ SOMETHING=/foo hg paths dupe = $TESTTMP/b#tip expand = /foo/bar #endif $ hg paths -q dupe expand $ hg paths dupe $TESTTMP/b#tip $ hg paths -q dupe $ hg paths unknown not found! [1] $ hg paths -q unknown [1] formatter output with paths: $ echo 'dupe:pushurl = https://example.com/dupe' >> .hg/hgrc $ hg paths -Tjson | sed 's|\\\\|\\|g' [ { "name": "dupe", "pushurl": "https://example.com/dupe", "url": "$TESTTMP/b#tip" }, { "name": "expand", "url": "$TESTTMP/a/$SOMETHING/bar" } ] $ hg paths -Tjson dupe | sed 's|\\\\|\\|g' [ { "name": "dupe", "pushurl": "https://example.com/dupe", "url": "$TESTTMP/b#tip" } ] $ hg paths -Tjson -q unknown [ ] [1] log template: (behaves as a {name: path-string} dict by default) $ hg log -rnull -T '{peerurls}\n' dupe=$TESTTMP/b#tip expand=$TESTTMP/a/$SOMETHING/bar $ hg log -rnull -T '{join(peerurls, "\n")}\n' dupe=$TESTTMP/b#tip expand=$TESTTMP/a/$SOMETHING/bar $ hg log -rnull -T '{peerurls % "{name}: {url}\n"}' dupe: $TESTTMP/b#tip expand: $TESTTMP/a/$SOMETHING/bar $ hg log -rnull -T '{get(peerurls, "dupe")}\n' $TESTTMP/b#tip (sub options can be populated by map/dot operation) $ hg log -rnull \ > -T '{get(peerurls, "dupe") % "url: {url}\npushurl: {pushurl}\n"}' url: $TESTTMP/b#tip pushurl: https://example.com/dupe $ hg log -rnull -T '{peerurls.dupe.pushurl}\n' https://example.com/dupe (in JSON, it's a dict of urls) $ hg log -rnull -T '{peerurls|json}\n' | sed 's|\\\\|/|g' {"dupe": "$TESTTMP/b#tip", "expand": "$TESTTMP/a/$SOMETHING/bar"} password should be masked in plain output, but not in machine-readable/template output: $ echo 'insecure = http://foo:insecure@example.com/' >> .hg/hgrc $ hg paths insecure http://foo:***@example.com/ $ hg paths -Tjson insecure [ { "name": "insecure", "url": "http://foo:insecure@example.com/" } ] $ hg log -rnull -T '{get(peerurls, "insecure")}\n' http://foo:insecure@example.com/ zeroconf wraps ui.configitems(), which shouldn't crash at least: $ hg paths --config extensions.zeroconf= dupe = $TESTTMP/b#tip dupe:pushurl = https://example.com/dupe expand = $TESTTMP/a/$SOMETHING/bar insecure = http://foo:***@example.com/ $ cd .. sub-options for an undeclared path are ignored $ hg init suboptions $ cd suboptions $ cat > .hg/hgrc << EOF > [paths] > path0 = https://example.com/path0 > path1:pushurl = https://example.com/path1 > EOF $ hg paths path0 = https://example.com/path0 unknown sub-options aren't displayed $ cat > .hg/hgrc << EOF > [paths] > path0 = https://example.com/path0 > path0:foo = https://example.com/path1 > EOF $ hg paths path0 = https://example.com/path0 :pushurl must be a URL $ cat > .hg/hgrc << EOF > [paths] > default = /path/to/nothing > default:pushurl = /not/a/url > EOF $ hg paths (paths.default:pushurl not a URL; ignoring) default = /path/to/nothing #fragment is not allowed in :pushurl $ cat > .hg/hgrc << EOF > [paths] > default = https://example.com/repo > invalid = https://example.com/repo > invalid:pushurl = https://example.com/repo#branch > EOF $ hg paths ("#fragment" in paths.invalid:pushurl not supported; ignoring) default = https://example.com/repo invalid = https://example.com/repo invalid:pushurl = https://example.com/repo $ cd .. 'file:' disables [paths] entries for clone destination $ cat >> $HGRCPATH <<EOF > [paths] > gpath1 = http://hg.example.com > EOF $ hg clone a gpath1 abort: cannot create new http repository [255] $ hg clone a file:gpath1 updating to branch default 0 files updated, 0 files merged, 0 files removed, 0 files unresolved $ cd gpath1 $ hg -q id 000000000000 $ cd ..