annotate mercurial/lock.py @ 1753:e6e70450edb9

Raise a different exception when the lock is not available When the filesystem is read-only or if we have some other error, there is no need to wait. Raise a lock.LockUnavailable exception.
author Benoit Boissinot <benoit.boissinot@ens-lyon.org>
date Mon, 20 Feb 2006 01:09:40 +0100
parents 59b3639df0a9
children e431344e604c
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1 # lock.py - simple locking scheme for mercurial
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2 #
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3 # Copyright 2005 Matt Mackall <mpm@selenic.com>
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4 #
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5 # This software may be used and distributed according to the terms
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6 # of the GNU General Public License, incorporated herein by reference.
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7
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8 import errno, os, time
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9 import util
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10
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11 class LockException(Exception):
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12 pass
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13 class LockHeld(LockException):
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14 pass
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15 class LockUnavailable(LockException):
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16 pass
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17
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18 class lock(object):
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19 def __init__(self, file, wait=1, releasefn=None):
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20 self.f = file
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21 self.held = 0
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22 self.wait = wait
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23 self.releasefn = releasefn
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24 self.lock()
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25
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26 def __del__(self):
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27 self.release()
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28
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29 def lock(self):
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30 while 1:
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31 try:
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32 self.trylock()
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33 return 1
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34 except LockHeld, inst:
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35 if self.wait:
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36 time.sleep(1)
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37 continue
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38 raise inst
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39
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40 def trylock(self):
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41 pid = os.getpid()
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42 try:
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43 util.makelock(str(pid), self.f)
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44 self.held = 1
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45 except (OSError, IOError), why:
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46 if why.errno == errno.EEXIST:
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47 raise LockHeld(util.readlock(self.f))
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48 else:
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49 raise LockUnavailable(why)
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50
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51 def release(self):
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52 if self.held:
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53 self.held = 0
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54 if self.releasefn:
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55 self.releasefn()
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56 try:
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57 os.unlink(self.f)
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58 except: pass
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59