mercurial/lock.py
author FUJIWARA Katsunori <foozy@lares.dti.ne.jp>
Wed, 05 Nov 2014 23:24:47 +0900
changeset 23183 51c9196a6bd0
parent 23032 f484be02bd35
child 25660 328739ea70c3
permissions -rw-r--r--
largefiles: remove meaningless code path for "hg pull --rebase" This patch removes "--rebase" specific code path for "hg pull" in "overridepull", because previous patch makes it meaningless: now, "rebase.rebase" ("orig" invocation in this patch) can update/commit largefiles safely without "repo._isrebasing = True". As a side effect of removing "rebase.rebase" invocation in "overridepull", this patch removes "nothing to rebase ..." message in "test-largefiles.t", which is shown only when rebase extension is enabled AFTER largefiles: before this patch: 1. "dispatch" invokes "pullrebase" of rebase as "hg pull" at first, because rebase wraps "hg pull" later 2. "pullrebase" invokes "overridepull" of largefiles as "orig", even though rebase assumes that "orig" is "pull" of commands 3. "overridepull" executes "pull" and "rebase" directly 3.1 "pull" pulls changesets and creates new head "X" 3.2 "rebase" rebases current working parent "Y" on "X" 4. "overridepull" returns to "pullrebase" 5. "pullrebase" tries to rebase, but there is nothing to be done, because "Y" is already rebased on "X". then, it shows "nothing to rebase ..." after this patch: 1. "dispatch" invokes "pullrebase" of rebase as "hg pull" 2. "pullrebase" invokes "overridepull" of largefiles as "orig" 3. "overridepull" executes "pull" as "orig" 4. "overridepull" returns to "pullrebase" 5. revision "Y" is not yet rebased, so "pullrebase" doesn't shows "nothing to rebase ..." As another side effect of removing "rebase.rebase" invocation, this patch fixes issue3861, which occurs only when rebase extension is enabled BEFORE largefiles: before this patch: 1. "dispatch" invokes "overridepull" of largefiles at first, because largefiles wrap "hg pull" later 2. "overridepull" executes "pull" and "rebase" explicitly 2.1 "pull" pulls changesets and creates new head "X" 2.2 "rebase" rebases current working parent, but fails because no revision is checked out in issue3861 case 3. "overridepull" returns to "dispatch" with exit code 1 returned from "rebase" at (2.2) 4. "hg pull" terminates with exit code 1 unexpectedly after this patch: 1. "dispatch" invokes "overridepull" of largefiles at first 2. "overridepull" invokes "pullrebase" of rebase as "orig" 3. "pullrebase" invokes "pull" as "orig" 4. "pullrebase" invokes "rebase", and it fails 5. "pullrebase" returns to "overridepull" with exit code 0 (because "pullrebase" ignores result of "pull" and "rebase") 6. "overridepull" returns to "dispatch" with exit code 0 returned from "rebase" at (5) 7. "hg pull" terminates with exit code 0

# lock.py - simple advisory locking scheme for mercurial
#
# Copyright 2005, 2006 Matt Mackall <mpm@selenic.com>
#
# 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()