view mercurial/lock.py @ 23976:344939126579 stable

largefiles: don't interfere with logging normal files

The previous code was adding standin files to the matcher's file list when
neither the standin file nor the original existed in the context.  Somehow, this
was confusing the logging code into behaving differently from when the extension
wasn't loaded.

It seems that this was an attempt to support naming a directory that only
contains largefiles, as a test fails if the else clause is dropped entirely.
Therefore, only append the "standin" if it is a directory.  This was found by
running the test suite with --config extensions.largefiles=.

The first added test used to log an additional cset that wasn't logged normally.
The only relation it had to file 'a' is that 'a' was the source of a move, but
it isn't clear why having '.hglf/a' in the list causes this change:

    @@ -47,6 +47,11 @@

     Make sure largefiles doesn't interfere with logging a regular file
       $ hg log a --config extensions.largefiles=
    +  changeset:   3:2ca5ba701980
    +  user:        test
    +  date:        Thu Jan 01 00:00:04 1970 +0000
    +  summary:     d
    +
       changeset:   0:9161b9aeaf16
       user:        test
       date:        Thu Jan 01 00:00:01 1970 +0000

The second added test used to complain about a file not being in the parent
revision:

    @@ -1638,10 +1643,8 @@

     Ensure that largefiles doesn't intefere with following a normal file
       $ hg  --config extensions.largefiles= log -f d -T '{desc}' -G
    -  @  c
    -  |
    -  o  a
    -
    +  abort: cannot follow file not in parent revision: ".hglf/d"
    +  [255]
       $ hg log -f d/a -T '{desc}' -G
       @  c
       |

Note that there is still something fishy with the largefiles code, because when
using a glob pattern like this:

    $ hg log 'glob:sub/*'

the pattern list would contain '.hglf/glob:sub/*'.  None of the tests show this
(this test lives in test-largefiles.t at 1349), it was just something that I
noticed when the code was loaded up with print statements.

# lock.py - simple advisory locking scheme for mercurial
#
# Copyright 2005, 2006 Matt Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

import util, error
import errno, os, socket, time
import warnings

class lock(object):
    '''An advisory lock held by one process to control access to a set
    of files.  Non-cooperating processes or incorrectly written scripts
    can ignore Mercurial's locking scheme and stomp all over the
    repository, so don't do that.

    Typically used via localrepository.lock() to lock the repository
    store (.hg/store/) or localrepository.wlock() to lock everything
    else under .hg/.'''

    # lock is symlink on platforms that support it, file on others.

    # symlink is used because create of directory entry and contents
    # are atomic even over nfs.

    # old-style lock: symlink to pid
    # new-style lock: symlink to hostname:pid

    _host = None

    def __init__(self, vfs, file, timeout=-1, releasefn=None, desc=None):
        self.vfs = vfs
        self.f = file
        self.held = 0
        self.timeout = timeout
        self.releasefn = releasefn
        self.desc = desc
        self.postrelease  = []
        self.pid = os.getpid()
        self.delay = self.lock()

    def __del__(self):
        if self.held:
            warnings.warn("use lock.release instead of del lock",
                    category=DeprecationWarning,
                    stacklevel=2)

            # ensure the lock will be removed
            # even if recursive locking did occur
            self.held = 1

        self.release()

    def lock(self):
        timeout = self.timeout
        while True:
            try:
                self.trylock()
                return self.timeout - timeout
            except error.LockHeld, inst:
                if timeout != 0:
                    time.sleep(1)
                    if timeout > 0:
                        timeout -= 1
                    continue
                raise error.LockHeld(errno.ETIMEDOUT, inst.filename, self.desc,
                                     inst.locker)

    def trylock(self):
        if self.held:
            self.held += 1
            return
        if lock._host is None:
            lock._host = socket.gethostname()
        lockname = '%s:%s' % (lock._host, self.pid)
        while not self.held:
            try:
                self.vfs.makelock(lockname, self.f)
                self.held = 1
            except (OSError, IOError), why:
                if why.errno == errno.EEXIST:
                    locker = self.testlock()
                    if locker is not None:
                        raise error.LockHeld(errno.EAGAIN,
                                             self.vfs.join(self.f), self.desc,
                                             locker)
                else:
                    raise error.LockUnavailable(why.errno, why.strerror,
                                                why.filename, self.desc)

    def testlock(self):
        """return id of locker if lock is valid, else None.

        If old-style lock, we cannot tell what machine locker is on.
        with new-style lock, if locker is on this machine, we can
        see if locker is alive.  If locker is on this machine but
        not alive, we can safely break lock.

        The lock file is only deleted when None is returned.

        """
        try:
            locker = self.vfs.readlock(self.f)
        except (OSError, IOError), why:
            if why.errno == errno.ENOENT:
                return None
            raise
        try:
            host, pid = locker.split(":", 1)
        except ValueError:
            return locker
        if host != lock._host:
            return locker
        try:
            pid = int(pid)
        except ValueError:
            return locker
        if util.testpid(pid):
            return locker
        # if locker dead, break lock.  must do this with another lock
        # held, or can race and break valid lock.
        try:
            l = lock(self.vfs, self.f + '.break', timeout=0)
            self.vfs.unlink(self.f)
            l.release()
        except error.LockError:
            return locker

    def release(self):
        """release the lock and execute callback function if any

        If the lock has been acquired multiple times, the actual release is
        delayed to the last release call."""
        if self.held > 1:
            self.held -= 1
        elif self.held == 1:
            self.held = 0
            if os.getpid() != self.pid:
                # we forked, and are not the parent
                return
            try:
                if self.releasefn:
                    self.releasefn()
            finally:
                try:
                    self.vfs.unlink(self.f)
                except OSError:
                    pass
            for callback in self.postrelease:
                callback()

def release(*locks):
    for lock in locks:
        if lock is not None:
            lock.release()