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| 1 # Copyright 2013 The Chromium Authors. All rights reserved. | |
| 2 # Use of this source code is governed by a BSD-style license that can be | |
| 3 # found in the LICENSE file. | |
| 4 | |
| 5 """Thread and ThreadGroup that reraise exceptions on the main thread.""" | |
| 6 # pylint: disable=W0212 | |
| 7 | |
| 8 import logging | |
| 9 import sys | |
| 10 import threading | |
| 11 import traceback | |
| 12 | |
| 13 from pylib.utils import watchdog_timer | |
| 14 | |
| 15 | |
| 16 class TimeoutError(Exception): | |
| 17 """Module-specific timeout exception.""" | |
| 18 pass | |
| 19 | |
| 20 | |
| 21 def LogThreadStack(thread): | |
| 22 """Log the stack for the given thread. | |
| 23 | |
| 24 Args: | |
| 25 thread: a threading.Thread instance. | |
| 26 """ | |
| 27 stack = sys._current_frames()[thread.ident] | |
| 28 logging.critical('*' * 80) | |
| 29 logging.critical('Stack dump for thread %r', thread.name) | |
| 30 logging.critical('*' * 80) | |
| 31 for filename, lineno, name, line in traceback.extract_stack(stack): | |
| 32 logging.critical('File: "%s", line %d, in %s', filename, lineno, name) | |
| 33 if line: | |
| 34 logging.critical(' %s', line.strip()) | |
| 35 logging.critical('*' * 80) | |
| 36 | |
| 37 | |
| 38 class ReraiserThread(threading.Thread): | |
| 39 """Thread class that can reraise exceptions.""" | |
| 40 | |
| 41 def __init__(self, func, args=None, kwargs=None, name=None): | |
| 42 """Initialize thread. | |
| 43 | |
| 44 Args: | |
| 45 func: callable to call on a new thread. | |
| 46 args: list of positional arguments for callable, defaults to empty. | |
| 47 kwargs: dictionary of keyword arguments for callable, defaults to empty. | |
| 48 name: thread name, defaults to Thread-N. | |
| 49 """ | |
| 50 super(ReraiserThread, self).__init__(name=name) | |
| 51 if not args: | |
| 52 args = [] | |
| 53 if not kwargs: | |
| 54 kwargs = {} | |
| 55 self.daemon = True | |
| 56 self._func = func | |
| 57 self._args = args | |
| 58 self._kwargs = kwargs | |
| 59 self._ret = None | |
| 60 self._exc_info = None | |
| 61 | |
| 62 def ReraiseIfException(self): | |
| 63 """Reraise exception if an exception was raised in the thread.""" | |
| 64 if self._exc_info: | |
| 65 raise self._exc_info[0], self._exc_info[1], self._exc_info[2] | |
| 66 | |
| 67 def GetReturnValue(self): | |
| 68 """Reraise exception if present, otherwise get the return value.""" | |
| 69 self.ReraiseIfException() | |
| 70 return self._ret | |
| 71 | |
| 72 #override | |
| 73 def run(self): | |
| 74 """Overrides Thread.run() to add support for reraising exceptions.""" | |
| 75 try: | |
| 76 self._ret = self._func(*self._args, **self._kwargs) | |
| 77 except: # pylint: disable=W0702 | |
| 78 self._exc_info = sys.exc_info() | |
| 79 | |
| 80 | |
| 81 class ReraiserThreadGroup(object): | |
| 82 """A group of ReraiserThread objects.""" | |
| 83 | |
| 84 def __init__(self, threads=None): | |
| 85 """Initialize thread group. | |
| 86 | |
| 87 Args: | |
| 88 threads: a list of ReraiserThread objects; defaults to empty. | |
| 89 """ | |
| 90 if not threads: | |
| 91 threads = [] | |
| 92 self._threads = threads | |
| 93 | |
| 94 def Add(self, thread): | |
| 95 """Add a thread to the group. | |
| 96 | |
| 97 Args: | |
| 98 thread: a ReraiserThread object. | |
| 99 """ | |
| 100 self._threads.append(thread) | |
| 101 | |
| 102 def StartAll(self): | |
| 103 """Start all threads.""" | |
| 104 for thread in self._threads: | |
| 105 thread.start() | |
| 106 | |
| 107 def _JoinAll(self, watcher=None): | |
| 108 """Join all threads without stack dumps. | |
| 109 | |
| 110 Reraises exceptions raised by the child threads and supports breaking | |
| 111 immediately on exceptions raised on the main thread. | |
| 112 | |
| 113 Args: | |
| 114 watcher: Watchdog object providing timeout, by default waits forever. | |
| 115 """ | |
| 116 if watcher is None: | |
| 117 watcher = watchdog_timer.WatchdogTimer(None) | |
| 118 alive_threads = self._threads[:] | |
| 119 while alive_threads: | |
| 120 for thread in alive_threads[:]: | |
| 121 if watcher.IsTimedOut(): | |
| 122 raise TimeoutError('Timed out waiting for %d of %d threads.' % | |
| 123 (len(alive_threads), len(self._threads))) | |
| 124 # Allow the main thread to periodically check for interrupts. | |
| 125 thread.join(0.1) | |
| 126 if not thread.isAlive(): | |
| 127 alive_threads.remove(thread) | |
| 128 # All threads are allowed to complete before reraising exceptions. | |
| 129 for thread in self._threads: | |
| 130 thread.ReraiseIfException() | |
| 131 | |
| 132 def JoinAll(self, watcher=None): | |
| 133 """Join all threads. | |
| 134 | |
| 135 Reraises exceptions raised by the child threads and supports breaking | |
| 136 immediately on exceptions raised on the main thread. Unfinished threads' | |
| 137 stacks will be logged on watchdog timeout. | |
| 138 | |
| 139 Args: | |
| 140 watcher: Watchdog object providing timeout, by default waits forever. | |
| 141 """ | |
| 142 try: | |
| 143 self._JoinAll(watcher) | |
| 144 except TimeoutError: | |
| 145 for thread in (t for t in self._threads if t.isAlive()): | |
| 146 LogThreadStack(thread) | |
| 147 raise | |
| 148 | |
| 149 def GetAllReturnValues(self, watcher=None): | |
| 150 """Get all return values, joining all threads if necessary. | |
| 151 | |
| 152 Args: | |
| 153 watcher: same as in |JoinAll|. Only used if threads are alive. | |
| 154 """ | |
| 155 if any([t.isAlive() for t in self._threads]): | |
| 156 self.JoinAll(watcher) | |
| 157 return [t.GetReturnValue() for t in self._threads] | |
| 158 | |
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