view tests/test-eolfilename.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

#require eol-in-paths

https://bz.mercurial-scm.org/352

test issue352

  $ hg init foo
  $ cd foo
  $ A=`printf 'he\rllo'`
  $ echo foo > "$A"
  $ hg add
  adding he\r (no-eol) (esc)
  llo
  abort: '\n' and '\r' disallowed in filenames: 'he\rllo'
  [255]
  $ hg ci -A -m m
  adding he\r (no-eol) (esc)
  llo
  abort: '\n' and '\r' disallowed in filenames: 'he\rllo'
  [255]
  $ rm "$A"
  $ echo foo > "hell
  > o"
  $ hg add
  adding hell
  o
  abort: '\n' and '\r' disallowed in filenames: 'hell\no'
  [255]
  $ hg ci -A -m m
  adding hell
  o
  abort: '\n' and '\r' disallowed in filenames: 'hell\no'
  [255]
  $ echo foo > "$A"
  $ hg debugwalk -v
  * matcher:
  <alwaysmatcher>
  f  he\r (no-eol) (esc)
  llo  he\r (no-eol) (esc)
  llo
  f  hell
  o  hell
  o

  $ echo bla > quickfox
  $ hg add quickfox
  $ hg ci -m 2
  $ A=`printf 'quick\rfox'`
  $ hg cp quickfox "$A"
  abort: '\n' and '\r' disallowed in filenames: 'quick\rfox'
  [255]
  $ hg mv quickfox "$A"
  abort: '\n' and '\r' disallowed in filenames: 'quick\rfox'
  [255]

https://bz.mercurial-scm.org/2036

  $ cd ..

test issue2039

  $ hg init bar
  $ cd bar
  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > color =
  > [color]
  > mode = ansi
  > EOF
  $ A=`printf 'foo\nbar'`
  $ B=`printf 'foo\nbar.baz'`
  $ touch "$A"
  $ touch "$B"
  $ hg status --color=always
  \x1b[0;35;1;4m? \x1b[0m\x1b[0;35;1;4mfoo\x1b[0m (esc)
  \x1b[0;35;1;4mbar\x1b[0m (esc)
  \x1b[0;35;1;4m? \x1b[0m\x1b[0;35;1;4mfoo\x1b[0m (esc)
  \x1b[0;35;1;4mbar.baz\x1b[0m (esc)

  $ cd ..