code.delx.au - offlineimap/blob - offlineimap/threadutil.py

   1 # Copyright (C) 2002, 2003 John Goerzen
   2 # Thread support module
   3 # <jgoerzen@complete.org>
   4 #
   5 #    This program is free software; you can redistribute it and/or modify
   6 #    it under the terms of the GNU General Public License as published by
   7 #    the Free Software Foundation; either version 2 of the License, or
   8 #    (at your option) any later version.
   9 #
  10 #    This program is distributed in the hope that it will be useful,
  11 #    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 #    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 #    GNU General Public License for more details.
  14 #
  15 #    You should have received a copy of the GNU General Public License
  16 #    along with this program; if not, write to the Free Software
  17 #    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
  18
  19 from threading import *
  20 from StringIO import StringIO
  21 from Queue import Queue, Empty
  22 import sys, traceback, thread, time
  23 from offlineimap.ui import UIBase       # for getglobalui()
  24
  25 profiledir = None
  26
  27 def setprofiledir(newdir):
  28     global profiledir
  29     profiledir = newdir
  30
  31 ######################################################################
  32 # General utilities
  33 ######################################################################
  34
  35 def semaphorereset(semaphore, originalstate):
  36     """Wait until the semaphore gets back to its original state -- all acquired
  37     resources released."""
  38     for i in range(originalstate):
  39         semaphore.acquire()
  40     # Now release these.
  41     for i in range(originalstate):
  42         semaphore.release()
  43
  44 def semaphorewait(semaphore):
  45     semaphore.acquire()
  46     semaphore.release()
  47
  48 def threadsreset(threadlist):
  49     for thr in threadlist:
  50         thr.join()
  51
  52 class threadlist:
  53     def __init__(self):
  54         self.lock = Lock()
  55         self.list = []
  56
  57     def add(self, thread):
  58         self.lock.acquire()
  59         try:
  60             self.list.append(thread)
  61         finally:
  62             self.lock.release()
  63
  64     def remove(self, thread):
  65         self.lock.acquire()
  66         try:
  67             self.list.remove(thread)
  68         finally:
  69             self.lock.release()
  70
  71     def pop(self):
  72         self.lock.acquire()
  73         try:
  74             if not len(self.list):
  75                 return None
  76             return self.list.pop()
  77         finally:
  78             self.lock.release()
  79
  80     def reset(self):
  81         while 1:
  82             thread = self.pop()
  83             if not thread:
  84                 return
  85             thread.join()
  86
  87
  88 ######################################################################
  89 # Exit-notify threads
  90 ######################################################################
  91
  92 exitthreads = Queue(100)
  93 inited = 0
  94
  95 def initexitnotify():
  96     """Initialize the exit notify system.  This MUST be called from the
  97     SAME THREAD that will call monitorloop BEFORE it calls monitorloop.
  98     This SHOULD be called before the main thread starts any other
  99     ExitNotifyThreads, or else it may miss the ability to catch the exit
 100     status from them!"""
 101     pass
 102
 103 def exitnotifymonitorloop(callback):
 104     """Enter an infinite "monitoring" loop.  The argument, callback,
 105     defines the function to call when an ExitNotifyThread has terminated.
 106     That function is called with a single argument -- the ExitNotifyThread
 107     that has terminated.  The monitor will not continue to monitor for
 108     other threads until the function returns, so if it intends to perform
 109     long calculations, it should start a new thread itself -- but NOT
 110     an ExitNotifyThread, or else an infinite loop may result.  Furthermore,
 111     the monitor will hold the lock all the while the other thread is waiting.
 112     """
 113     global exitthreads
 114     while 1:                            # Loop forever.
 115         try:
 116             thrd = exitthreads.get(False)
 117             callback(thrd)
 118         except Empty:
 119             time.sleep(1)
 120
 121 def threadexited(thread):
 122     """Called when a thread exits."""
 123     ui = UIBase.getglobalui()
 124     if thread.getExitCause() == 'EXCEPTION':
 125         if isinstance(thread.getExitException(), SystemExit):
 126             # Bring a SystemExit into the main thread.
 127             # Do not send it back to UI layer right now.
 128             # Maybe later send it to ui.terminate?
 129             raise SystemExit
 130         ui.threadException(thread)      # Expected to terminate
 131         sys.exit(100)                   # Just in case...
 132         os._exit(100)
 133     elif thread.getExitMessage() == 'SYNC_WITH_TIMER_TERMINATE':
 134         ui.terminate()
 135         # Just in case...
 136         sys.exit(100)
 137         os._exit(100)
 138     else:
 139         ui.threadExited(thread)
 140
 141 class ExitNotifyThread(Thread):
 142     """This class is designed to alert a "monitor" to the fact that a thread has
 143     exited and to provide for the ability for it to find out why."""
 144     def run(self):
 145         global exitthreads, profiledir
 146         self.threadid = thread.get_ident()
 147         try:
 148             if not profiledir:          # normal case
 149                 Thread.run(self)
 150             else:
 151                 import profile
 152                 prof = profile.Profile()
 153                 try:
 154                     prof = prof.runctx("Thread.run(self)", globals(), locals())
 155                 except SystemExit:
 156                     pass
 157                 prof.dump_stats( \
 158                             profiledir + "/" + str(self.threadid) + "_" + \
 159                             self.getName() + ".prof")
 160         except:
 161             self.setExitCause('EXCEPTION')
 162             self.setExitException(sys.exc_info()[1])
 163             sbuf = StringIO()
 164             traceback.print_exc(file = sbuf)
 165             self.setExitStackTrace(sbuf.getvalue())
 166         else:
 167             self.setExitCause('NORMAL')
 168         if not hasattr(self, 'exitmessage'):
 169             self.setExitMessage(None)
 170
 171         exitthreads.put(self, True)
 172
 173     def setExitCause(self, cause):
 174         self.exitcause = cause
 175     def getExitCause(self):
 176         """Returns the cause of the exit, one of:
 177         'EXCEPTION' -- the thread aborted because of an exception
 178         'NORMAL' -- normal termination."""
 179         return self.exitcause
 180     def setExitException(self, exc):
 181         self.exitexception = exc
 182     def getExitException(self):
 183         """If getExitCause() is 'EXCEPTION', holds the value from
 184         sys.exc_info()[1] for this exception."""
 185         return self.exitexception
 186     def setExitStackTrace(self, st):
 187         self.exitstacktrace = st
 188     def getExitStackTrace(self):
 189         """If getExitCause() is 'EXCEPTION', returns a string representing
 190         the stack trace for this exception."""
 191         return self.exitstacktrace
 192     def setExitMessage(self, msg):
 193         """Sets the exit message to be fetched by a subsequent call to
 194         getExitMessage.  This message may be any object or type except
 195         None."""
 196         self.exitmessage = msg
 197     def getExitMessage(self):
 198         """For any exit cause, returns the message previously set by
 199         a call to setExitMessage(), or None if there was no such message
 200         set."""
 201         return self.exitmessage
 202
 203
 204 ######################################################################
 205 # Instance-limited threads
 206 ######################################################################
 207
 208 instancelimitedsems = {}
 209 instancelimitedlock = Lock()
 210
 211 def initInstanceLimit(instancename, instancemax):
 212     """Initialize the instance-limited thread implementation to permit
 213     up to intancemax threads with the given instancename."""
 214     instancelimitedlock.acquire()
 215     if not instancelimitedsems.has_key(instancename):
 216         instancelimitedsems[instancename] = BoundedSemaphore(instancemax)
 217     instancelimitedlock.release()
 218
 219 class InstanceLimitedThread(ExitNotifyThread):
 220     def __init__(self, instancename, *args, **kwargs):
 221         self.instancename = instancename
 222
 223         apply(ExitNotifyThread.__init__, (self,) + args, kwargs)
 224
 225     def start(self):
 226         instancelimitedsems[self.instancename].acquire()
 227         ExitNotifyThread.start(self)
 228
 229     def run(self):
 230         try:
 231             ExitNotifyThread.run(self)
 232         finally:
 233             instancelimitedsems[self.instancename].release()
 234
 235
 236 ######################################################################
 237 # Multi-lock -- capable of handling a single thread requesting a lock
 238 # multiple times
 239 ######################################################################
 240
 241 class MultiLock:
 242     def __init__(self):
 243         self.lock = Lock()
 244         self.statuslock = Lock()
 245         self.locksheld = {}
 246
 247     def acquire(self):
 248         """Obtain a lock.  Provides nice support for a single
 249         thread trying to lock it several times -- as may be the case
 250         if one I/O-using object calls others, while wanting to make it all
 251         an atomic operation.  Keeps a "lock request count" for the current
 252         thread, and acquires the lock when it goes above zero, releases when
 253         it goes below one.
 254
 255         This call is always blocking."""
 256
 257         # First, check to see if this thread already has a lock.
 258         # If so, increment the lock count and just return.
 259         self.statuslock.acquire()
 260         try:
 261             threadid = thread.get_ident()
 262
 263             if threadid in self.locksheld:
 264                 self.locksheld[threadid] += 1
 265                 return
 266             else:
 267                 # This is safe because it is a per-thread structure
 268                 self.locksheld[threadid] = 1
 269         finally:
 270             self.statuslock.release()
 271         self.lock.acquire()
 272
 273     def release(self):
 274         self.statuslock.acquire()
 275         try:
 276             threadid = thread.get_ident()
 277             if self.locksheld[threadid] > 1:
 278                 self.locksheld[threadid] -= 1
 279                 return
 280             else:
 281                 del self.locksheld[threadid]
 282                 self.lock.release()
 283         finally:
 284             self.statuslock.release()
 285
 286