Mercurial > hg
view tests/test-filebranch.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 | 07e181ed82ef |
children | 42d2b31cee0b |
line wrap: on
line source
This test makes sure that we don't mark a file as merged with its ancestor when we do a merge. $ cat <<EOF > merge > from __future__ import print_function > import sys, os > print("merging for", os.path.basename(sys.argv[1])) > EOF $ HGMERGE="\"$PYTHON\" ../merge"; export HGMERGE Creating base: $ hg init a $ cd a $ echo 1 > foo $ echo 1 > bar $ echo 1 > baz $ echo 1 > quux $ hg add foo bar baz quux $ hg commit -m "base" $ cd .. $ hg clone a b updating to branch default 4 files updated, 0 files merged, 0 files removed, 0 files unresolved Creating branch a: $ cd a $ echo 2a > foo $ echo 2a > bar $ hg commit -m "branch a" Creating branch b: $ cd .. $ cd b $ echo 2b > foo $ echo 2b > baz $ hg commit -m "branch b" We shouldn't have anything but n state here: $ hg debugstate --no-dates | grep -v "^n" [1] Merging: $ hg pull ../a pulling from ../a searching for changes adding changesets adding manifests adding file changes added 1 changesets with 2 changes to 2 files (+1 heads) new changesets bdd988058d16 (run 'hg heads' to see heads, 'hg merge' to merge) $ hg merge -v resolving manifests getting bar merging foo merging for foo 1 files updated, 1 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ echo 2m > foo $ echo 2b > baz $ echo new > quux $ hg ci -m "merge" main: we should have a merge here: $ hg debugindex --changelog rev linkrev nodeid p1 p2 0 0 cdca01651b96 000000000000 000000000000 1 1 f6718a9cb7f3 cdca01651b96 000000000000 2 2 bdd988058d16 cdca01651b96 000000000000 3 3 d8a521142a3c f6718a9cb7f3 bdd988058d16 log should show foo and quux changed: $ hg log -v -r tip changeset: 3:d8a521142a3c tag: tip parent: 1:f6718a9cb7f3 parent: 2:bdd988058d16 user: test date: Thu Jan 01 00:00:00 1970 +0000 files: foo quux description: merge foo: we should have a merge here: $ hg debugindex foo rev linkrev nodeid p1 p2 0 0 b8e02f643373 000000000000 000000000000 1 1 2ffeddde1b65 b8e02f643373 000000000000 2 2 33d1fb69067a b8e02f643373 000000000000 3 3 aa27919ee430 2ffeddde1b65 33d1fb69067a bar: we should not have a merge here: $ hg debugindex bar rev linkrev nodeid p1 p2 0 0 b8e02f643373 000000000000 000000000000 1 2 33d1fb69067a b8e02f643373 000000000000 baz: we should not have a merge here: $ hg debugindex baz rev linkrev nodeid p1 p2 0 0 b8e02f643373 000000000000 000000000000 1 1 2ffeddde1b65 b8e02f643373 000000000000 quux: we should not have a merge here: $ hg debugindex quux rev linkrev nodeid p1 p2 0 0 b8e02f643373 000000000000 000000000000 1 3 6128c0f33108 b8e02f643373 000000000000 Manifest entries should match tips of all files: $ hg manifest --debug 33d1fb69067a0139622a3fa3b7ba1cdb1367972e 644 bar 2ffeddde1b65b4827f6746174a145474129fa2ce 644 baz aa27919ee4303cfd575e1fb932dd64d75aa08be4 644 foo 6128c0f33108e8cfbb4e0824d13ae48b466d7280 644 quux Everything should be clean now: $ hg status $ hg verify checking changesets checking manifests crosschecking files in changesets and manifests checking files checked 4 changesets with 10 changes to 4 files $ cd ..