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lock: fix race in lock-breaking code...
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
Matt Harbison - - Load All Authors

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filesets.txt
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Mercurial supports a functional language for selecting a set of
files.
Like other file patterns, this pattern type is indicated by a prefix,
'set:'. The language supports a number of predicates which are joined
by infix operators. Parenthesis can be used for grouping.
Identifiers such as filenames or patterns must be quoted with single
or double quotes if they contain characters outside of
``[.*{}[]?/\_a-zA-Z0-9\x80-\xff]`` or if they match one of the
predefined predicates. This generally applies to file patterns other
than globs and arguments for predicates. Pattern prefixes such as
``path:`` may be specified without quoting.
Special characters can be used in quoted identifiers by escaping them,
e.g., ``\n`` is interpreted as a newline. To prevent them from being
interpreted, strings can be prefixed with ``r``, e.g. ``r'...'``.
See also :hg:`help patterns`.
Operators
=========
There is a single prefix operator:
``not x``
Files not in x. Short form is ``! x``.
These are the supported infix operators:
``x and y``
The intersection of files in x and y. Short form is ``x & y``.
``x or y``
The union of files in x and y. There are two alternative short
forms: ``x | y`` and ``x + y``.
``x - y``
Files in x but not in y.
Predicates
==========
The following predicates are supported:
.. predicatesmarker
Examples
========
Some sample queries:
- Show status of files that appear to be binary in the working directory::
hg status -A "set:binary()"
- Forget files that are in .hgignore but are already tracked::
hg forget "set:hgignore() and not ignored()"
- Find text files that contain a string::
hg files "set:grep(magic) and not binary()"
- Find C files in a non-standard encoding::
hg files "set:**.c and not encoding('UTF-8')"
- Revert copies of large binary files::
hg revert "set:copied() and binary() and size('>1M')"
- Revert files that were added to the working directory::
hg revert "set:revs('wdir()', added())"
- Remove files listed in foo.lst that contain the letter a or b::
hg remove "set: listfile:foo.lst and (**a* or **b*)"