+++ /dev/null
-"""CVS locking algorithm.\r
-\r
-CVS locking strategy\r
-====================\r
-\r
-As reverse engineered from the CVS 1.3 sources (file lock.c):\r
-\r
-- Locking is done on a per repository basis (but a process can hold\r
-write locks for multiple directories); all lock files are placed in\r
-the repository and have names beginning with "#cvs.".\r
-\r
-- Before even attempting to lock, a file "#cvs.tfl.<pid>" is created\r
-(and removed again), to test that we can write the repository. [The\r
-algorithm can still be fooled (1) if the repository's mode is changed\r
-while attempting to lock; (2) if this file exists and is writable but\r
-the directory is not.]\r
-\r
-- While creating the actual read/write lock files (which may exist for\r
-a long time), a "meta-lock" is held. The meta-lock is a directory\r
-named "#cvs.lock" in the repository. The meta-lock is also held while\r
-a write lock is held.\r
-\r
-- To set a read lock:\r
-\r
- - acquire the meta-lock\r
- - create the file "#cvs.rfl.<pid>"\r
- - release the meta-lock\r
-\r
-- To set a write lock:\r
-\r
- - acquire the meta-lock\r
- - check that there are no files called "#cvs.rfl.*"\r
- - if there are, release the meta-lock, sleep, try again\r
- - create the file "#cvs.wfl.<pid>"\r
-\r
-- To release a write lock:\r
-\r
- - remove the file "#cvs.wfl.<pid>"\r
- - rmdir the meta-lock\r
-\r
-- To release a read lock:\r
-\r
- - remove the file "#cvs.rfl.<pid>"\r
-\r
-\r
-Additional notes\r
-----------------\r
-\r
-- A process should read-lock at most one repository at a time.\r
-\r
-- A process may write-lock as many repositories as it wishes (to avoid\r
-deadlocks, I presume it should always lock them top-down in the\r
-directory hierarchy).\r
-\r
-- A process should make sure it removes all its lock files and\r
-directories when it crashes.\r
-\r
-- Limitation: one user id should not be committing files into the same\r
-repository at the same time.\r
-\r
-\r
-Turn this into Python code\r
---------------------------\r
-\r
-rl = ReadLock(repository, waittime)\r
-\r
-wl = WriteLock(repository, waittime)\r
-\r
-list = MultipleWriteLock([repository1, repository2, ...], waittime)\r
-\r
-"""\r
-\r
-\r
-import os\r
-import time\r
-import stat\r
-import pwd\r
-\r
-\r
-# Default wait time\r
-DELAY = 10\r
-\r
-\r
-# XXX This should be the same on all Unix versions\r
-EEXIST = 17\r
-\r
-\r
-# Files used for locking (must match cvs.h in the CVS sources)\r
-CVSLCK = "#cvs.lck"\r
-CVSRFL = "#cvs.rfl."\r
-CVSWFL = "#cvs.wfl."\r
-\r
-\r
-class Error:\r
-\r
- def __init__(self, msg):\r
- self.msg = msg\r
-\r
- def __repr__(self):\r
- return repr(self.msg)\r
-\r
- def __str__(self):\r
- return str(self.msg)\r
-\r
-\r
-class Locked(Error):\r
- pass\r
-\r
-\r
-class Lock:\r
-\r
- def __init__(self, repository = ".", delay = DELAY):\r
- self.repository = repository\r
- self.delay = delay\r
- self.lockdir = None\r
- self.lockfile = None\r
- pid = repr(os.getpid())\r
- self.cvslck = self.join(CVSLCK)\r
- self.cvsrfl = self.join(CVSRFL + pid)\r
- self.cvswfl = self.join(CVSWFL + pid)\r
-\r
- def __del__(self):\r
- print "__del__"\r
- self.unlock()\r
-\r
- def setlockdir(self):\r
- while 1:\r
- try:\r
- self.lockdir = self.cvslck\r
- os.mkdir(self.cvslck, 0777)\r
- return\r
- except os.error, msg:\r
- self.lockdir = None\r
- if msg[0] == EEXIST:\r
- try:\r
- st = os.stat(self.cvslck)\r
- except os.error:\r
- continue\r
- self.sleep(st)\r
- continue\r
- raise Error("failed to lock %s: %s" % (\r
- self.repository, msg))\r
-\r
- def unlock(self):\r
- self.unlockfile()\r
- self.unlockdir()\r
-\r
- def unlockfile(self):\r
- if self.lockfile:\r
- print "unlink", self.lockfile\r
- try:\r
- os.unlink(self.lockfile)\r
- except os.error:\r
- pass\r
- self.lockfile = None\r
-\r
- def unlockdir(self):\r
- if self.lockdir:\r
- print "rmdir", self.lockdir\r
- try:\r
- os.rmdir(self.lockdir)\r
- except os.error:\r
- pass\r
- self.lockdir = None\r
-\r
- def sleep(self, st):\r
- sleep(st, self.repository, self.delay)\r
-\r
- def join(self, name):\r
- return os.path.join(self.repository, name)\r
-\r
-\r
-def sleep(st, repository, delay):\r
- if delay <= 0:\r
- raise Locked(st)\r
- uid = st[stat.ST_UID]\r
- try:\r
- pwent = pwd.getpwuid(uid)\r
- user = pwent[0]\r
- except KeyError:\r
- user = "uid %d" % uid\r
- print "[%s]" % time.ctime(time.time())[11:19],\r
- print "Waiting for %s's lock in" % user, repository\r
- time.sleep(delay)\r
-\r
-\r
-class ReadLock(Lock):\r
-\r
- def __init__(self, repository, delay = DELAY):\r
- Lock.__init__(self, repository, delay)\r
- ok = 0\r
- try:\r
- self.setlockdir()\r
- self.lockfile = self.cvsrfl\r
- fp = open(self.lockfile, 'w')\r
- fp.close()\r
- ok = 1\r
- finally:\r
- if not ok:\r
- self.unlockfile()\r
- self.unlockdir()\r
-\r
-\r
-class WriteLock(Lock):\r
-\r
- def __init__(self, repository, delay = DELAY):\r
- Lock.__init__(self, repository, delay)\r
- self.setlockdir()\r
- while 1:\r
- uid = self.readers_exist()\r
- if not uid:\r
- break\r
- self.unlockdir()\r
- self.sleep(uid)\r
- self.lockfile = self.cvswfl\r
- fp = open(self.lockfile, 'w')\r
- fp.close()\r
-\r
- def readers_exist(self):\r
- n = len(CVSRFL)\r
- for name in os.listdir(self.repository):\r
- if name[:n] == CVSRFL:\r
- try:\r
- st = os.stat(self.join(name))\r
- except os.error:\r
- continue\r
- return st\r
- return None\r
-\r
-\r
-def MultipleWriteLock(repositories, delay = DELAY):\r
- while 1:\r
- locks = []\r
- for r in repositories:\r
- try:\r
- locks.append(WriteLock(r, 0))\r
- except Locked, instance:\r
- del locks\r
- break\r
- else:\r
- break\r
- sleep(instance.msg, r, delay)\r
- return list\r
-\r
-\r
-def test():\r
- import sys\r
- if sys.argv[1:]:\r
- repository = sys.argv[1]\r
- else:\r
- repository = "."\r
- rl = None\r
- wl = None\r
- try:\r
- print "attempting write lock ..."\r
- wl = WriteLock(repository)\r
- print "got it."\r
- wl.unlock()\r
- print "attempting read lock ..."\r
- rl = ReadLock(repository)\r
- print "got it."\r
- rl.unlock()\r
- finally:\r
- print [1]\r
- sys.exc_traceback = None\r
- print [2]\r
- if rl:\r
- rl.unlock()\r
- print [3]\r
- if wl:\r
- wl.unlock()\r
- print [4]\r
- rl = None\r
- print [5]\r
- wl = None\r
- print [6]\r
-\r
-\r
-if __name__ == '__main__':\r
- test()\r
projects / mirror_edk2.git / blobdiff