view tests/test-url-rev.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

Test basic functionality of url#rev syntax

  $ hg init repo
  $ cd repo
  $ echo a > a
  $ hg ci -qAm 'add a'
  $ hg branch foo
  marked working directory as branch foo
  (branches are permanent and global, did you want a bookmark?)
  $ echo >> a
  $ hg ci -m 'change a'
  $ cd ..

  $ hg clone 'repo#foo' clone
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 1 files
  new changesets 1f0dee641bb7:cd2a86ecc814
  updating to branch foo
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg --cwd clone heads
  changeset:   1:cd2a86ecc814
  branch:      foo
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     change a
  
  changeset:   0:1f0dee641bb7
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add a
  
  $ hg --cwd clone parents
  changeset:   1:cd2a86ecc814
  branch:      foo
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     change a
  
  $ cat clone/.hg/hgrc
  # example repository config (see 'hg help config' for more info)
  [paths]
  default = $TESTTMP/repo#foo
  
  # path aliases to other clones of this repo in URLs or filesystem paths
  # (see 'hg help config.paths' for more info)
  #
  # default:pushurl = ssh://[e-mail]/hg/jdoes-fork
  # my-fork         = ssh://[e-mail]/hg/jdoes-fork
  # my-clone        = /home/jdoe/jdoes-clone
  
  [ui]
  # name and email (local to this repository, optional), e.g.
  # username = Jane Doe <[e-mail]>

Changing original repo:

  $ cd repo

  $ echo >> a
  $ hg ci -m 'new head of branch foo'

  $ hg up -qC default
  $ echo bar > bar
  $ hg ci -qAm 'add bar'

  $ hg log
  changeset:   3:4cd725637392
  tag:         tip
  parent:      0:1f0dee641bb7
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add bar
  
  changeset:   2:faba9097cad4
  branch:      foo
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     new head of branch foo
  
  changeset:   1:cd2a86ecc814
  branch:      foo
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     change a
  
  changeset:   0:1f0dee641bb7
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add a
  
  $ hg -q outgoing '../clone'
  2:faba9097cad4
  3:4cd725637392
  $ hg summary --remote --config paths.default='../clone'
  parent: 3:4cd725637392 tip
   add bar
  branch: default
  commit: (clean)
  update: (current)
  phases: 4 draft
  remote: 2 outgoing
  $ hg -q outgoing '../clone#foo'
  2:faba9097cad4
  $ hg summary --remote --config paths.default='../clone#foo'
  parent: 3:4cd725637392 tip
   add bar
  branch: default
  commit: (clean)
  update: (current)
  phases: 4 draft
  remote: 1 outgoing

  $ hg -q --cwd ../clone incoming '../repo#foo'
  2:faba9097cad4
  $ hg --cwd ../clone summary --remote --config paths.default='../repo#foo'
  parent: 1:cd2a86ecc814 tip
   change a
  branch: foo
  commit: (clean)
  update: (current)
  remote: 1 or more incoming

  $ hg -q push '../clone#foo'

  $ hg --cwd ../clone heads
  changeset:   2:faba9097cad4
  branch:      foo
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     new head of branch foo
  
  changeset:   0:1f0dee641bb7
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add a
  
  $ hg -q --cwd ../clone incoming '../repo#foo'
  [1]
  $ hg --cwd ../clone summary --remote --config paths.default='../repo#foo'
  parent: 1:cd2a86ecc814 
   change a
  branch: foo
  commit: (clean)
  update: 1 new changesets (update)
  remote: (synced)

  $ cd ..

  $ cd clone
  $ hg rollback
  repository tip rolled back to revision 1 (undo push)

  $ hg -q incoming
  2:faba9097cad4

  $ hg -q pull

  $ hg heads
  changeset:   2:faba9097cad4
  branch:      foo
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     new head of branch foo
  
  changeset:   0:1f0dee641bb7
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add a
  
Pull should not have updated:

  $ hg parents -q
  1:cd2a86ecc814

Going back to the default branch:

  $ hg up -C 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg parents
  changeset:   0:1f0dee641bb7
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add a
  
No new revs, no update:

  $ hg pull -qu

  $ hg parents -q
  0:1f0dee641bb7

  $ hg rollback
  repository tip rolled back to revision 1 (undo pull)

  $ hg parents -q
  0:1f0dee641bb7

Pull -u takes us back to branch foo:

  $ hg pull -qu

  $ hg parents
  changeset:   2:faba9097cad4
  branch:      foo
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     new head of branch foo
  
  $ hg rollback
  repository tip rolled back to revision 1 (undo pull)
  working directory now based on revision 0

  $ hg up -C 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg parents -q
  0:1f0dee641bb7

  $ hg heads -q
  1:cd2a86ecc814
  0:1f0dee641bb7

  $ hg pull -qur default default

  $ hg parents
  changeset:   3:4cd725637392
  tag:         tip
  parent:      0:1f0dee641bb7
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add bar
  
  $ hg heads
  changeset:   3:4cd725637392
  tag:         tip
  parent:      0:1f0dee641bb7
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add bar
  
  changeset:   2:faba9097cad4
  branch:      foo
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     new head of branch foo
  
Test handling of invalid urls

  $ hg id http://foo/?bar
  abort: unsupported URL component: "bar"
  [255]

  $ cd ..

Test handling common incoming revisions between "default" and
"default-push"

  $ hg -R clone rollback
  repository tip rolled back to revision 1 (undo pull)
  working directory now based on revision 0

  $ cd repo

  $ hg update -q -C default
  $ echo modified >> bar
  $ hg commit -m "new head to push current default head"
  $ hg -q push -r ".^1" '../clone'

  $ hg -q outgoing '../clone'
  2:faba9097cad4
  4:d515801a8f3d

  $ hg summary --remote --config paths.default='../clone#default' --config paths.default-push='../clone#foo'
  parent: 4:d515801a8f3d tip
   new head to push current default head
  branch: default
  commit: (clean)
  update: (current)
  phases: 1 draft
  remote: 1 outgoing

  $ hg summary --remote --config paths.default='../clone#foo' --config paths.default-push='../clone'
  parent: 4:d515801a8f3d tip
   new head to push current default head
  branch: default
  commit: (clean)
  update: (current)
  phases: 1 draft
  remote: 2 outgoing

  $ hg summary --remote --config paths.default='../clone' --config paths.default-push='../clone#foo'
  parent: 4:d515801a8f3d tip
   new head to push current default head
  branch: default
  commit: (clean)
  update: (current)
  phases: 1 draft
  remote: 1 outgoing

  $ hg clone -q -r 0 . ../another
  $ hg -q outgoing '../another#default'
  3:4cd725637392
  4:d515801a8f3d

  $ hg summary --remote --config paths.default='../another#default' --config paths.default-push='../clone#default'
  parent: 4:d515801a8f3d tip
   new head to push current default head
  branch: default
  commit: (clean)
  update: (current)
  phases: 1 draft
  remote: 1 outgoing

  $ cd ..

Test url#rev syntax of local destination path, which should be taken as
a 'url#rev' path

  $ hg clone repo '#foo'
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg root -R '#foo'
  $TESTTMP/#foo