Mercurial > hg > mercurial-crew-with-dirclash
view mercurial/lock.py @ 4100:c30c922f907a
Modify qpush/qpop idempotent operations to return success
Modify qpush/qpop such that idempotent instances of the operations
return success. That is, repeated qpush -a, qpop -a, qpush patch-name
or qpop patch-name will return success. The end goal of each of these
operations is to reach a particular state. Whether or not the patches
were already applied does not affect that state or operation status.
Likewise, be careful to retain the error status on a qpush/qpop
without arguments when the end/beginning of the series has been
reached.
author | Ben Thomas <bthomas@virtualiron.com> |
---|---|
date | Tue, 13 Feb 2007 08:54:48 -0500 |
parents | abaee83ce0a6 |
children | 3e25a6eb5c9a |
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# lock.py - simple 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, incorporated herein by reference. import errno, os, socket, time, util class LockException(IOError): def __init__(self, errno, strerror, filename, desc): IOError.__init__(self, errno, strerror, filename) self.desc = desc class LockHeld(LockException): def __init__(self, errno, filename, desc, locker): LockException.__init__(self, errno, 'Lock held', filename, desc) self.locker = locker class LockUnavailable(LockException): pass class lock(object): # 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 def __init__(self, file, timeout=-1, releasefn=None, desc=None): self.f = file self.held = 0 self.timeout = timeout self.releasefn = releasefn self.id = None self.host = None self.pid = None self.desc = desc self.lock() def __del__(self): self.release() def lock(self): timeout = self.timeout while 1: try: self.trylock() return 1 except LockHeld, inst: if timeout != 0: time.sleep(1) if timeout > 0: timeout -= 1 continue raise LockHeld(errno.ETIMEDOUT, inst.filename, self.desc, inst.locker) def trylock(self): if self.id is None: self.host = socket.gethostname() self.pid = os.getpid() self.id = '%s:%s' % (self.host, self.pid) while not self.held: try: util.makelock(self.id, self.f) self.held = 1 except (OSError, IOError), why: if why.errno == errno.EEXIST: locker = self.testlock() if locker is not None: raise LockHeld(errno.EAGAIN, self.f, self.desc, locker) else: raise 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. """ locker = util.readlock(self.f) try: host, pid = locker.split(":", 1) except ValueError: return locker if host != self.host: return locker try: pid = int(pid) except: 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.f + '.break') l.trylock() os.unlink(self.f) l.release() except (LockHeld, LockUnavailable): return locker def release(self): if self.held: self.held = 0 if self.releasefn: self.releasefn() try: os.unlink(self.f) except: pass