431 lines
16 KiB
Python
431 lines
16 KiB
Python
# MIT License
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#
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# Copyright The SCons Foundation
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#
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# Permission is hereby granted, free of charge, to any person obtaining
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# a copy of this software and associated documentation files (the
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# "Software"), to deal in the Software without restriction, including
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# without limitation the rights to use, copy, modify, merge, publish,
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# distribute, sublicense, and/or sell copies of the Software, and to
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# permit persons to whom the Software is furnished to do so, subject to
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# the following conditions:
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#
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# The above copyright notice and this permission notice shall be included
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# in all copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
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# KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
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# WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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"""Serial and Parallel classes to execute build tasks.
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The Jobs class provides a higher level interface to start,
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stop, and wait on jobs.
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"""
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import SCons.compat
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import os
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import signal
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import SCons.Errors
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# The default stack size (in kilobytes) of the threads used to execute
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# jobs in parallel.
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#
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# We use a stack size of 256 kilobytes. The default on some platforms
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# is too large and prevents us from creating enough threads to fully
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# parallelized the build. For example, the default stack size on linux
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# is 8 MBytes.
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explicit_stack_size = None
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default_stack_size = 256
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interrupt_msg = 'Build interrupted.'
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class InterruptState:
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def __init__(self):
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self.interrupted = False
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def set(self):
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self.interrupted = True
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def __call__(self):
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return self.interrupted
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class Jobs:
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"""An instance of this class initializes N jobs, and provides
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methods for starting, stopping, and waiting on all N jobs.
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"""
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def __init__(self, num, taskmaster):
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"""
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Create 'num' jobs using the given taskmaster.
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If 'num' is 1 or less, then a serial job will be used,
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otherwise a parallel job with 'num' worker threads will
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be used.
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The 'num_jobs' attribute will be set to the actual number of jobs
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allocated. If more than one job is requested but the Parallel
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class can't do it, it gets reset to 1. Wrapping interfaces that
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care should check the value of 'num_jobs' after initialization.
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"""
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self.job = None
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if num > 1:
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stack_size = explicit_stack_size
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if stack_size is None:
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stack_size = default_stack_size
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try:
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self.job = Parallel(taskmaster, num, stack_size)
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self.num_jobs = num
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except NameError:
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pass
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if self.job is None:
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self.job = Serial(taskmaster)
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self.num_jobs = 1
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def run(self, postfunc=lambda: None):
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"""Run the jobs.
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postfunc() will be invoked after the jobs has run. It will be
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invoked even if the jobs are interrupted by a keyboard
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interrupt (well, in fact by a signal such as either SIGINT,
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SIGTERM or SIGHUP). The execution of postfunc() is protected
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against keyboard interrupts and is guaranteed to run to
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completion."""
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self._setup_sig_handler()
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try:
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self.job.start()
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finally:
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postfunc()
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self._reset_sig_handler()
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def were_interrupted(self):
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"""Returns whether the jobs were interrupted by a signal."""
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return self.job.interrupted()
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def _setup_sig_handler(self):
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"""Setup an interrupt handler so that SCons can shutdown cleanly in
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various conditions:
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a) SIGINT: Keyboard interrupt
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b) SIGTERM: kill or system shutdown
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c) SIGHUP: Controlling shell exiting
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We handle all of these cases by stopping the taskmaster. It
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turns out that it's very difficult to stop the build process
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by throwing asynchronously an exception such as
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KeyboardInterrupt. For example, the python Condition
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variables (threading.Condition) and queues do not seem to be
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asynchronous-exception-safe. It would require adding a whole
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bunch of try/finally block and except KeyboardInterrupt all
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over the place.
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Note also that we have to be careful to handle the case when
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SCons forks before executing another process. In that case, we
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want the child to exit immediately.
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"""
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def handler(signum, stack, self=self, parentpid=os.getpid()):
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if os.getpid() == parentpid:
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self.job.taskmaster.stop()
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self.job.interrupted.set()
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else:
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os._exit(2)
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self.old_sigint = signal.signal(signal.SIGINT, handler)
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self.old_sigterm = signal.signal(signal.SIGTERM, handler)
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try:
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self.old_sighup = signal.signal(signal.SIGHUP, handler)
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except AttributeError:
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pass
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def _reset_sig_handler(self):
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"""Restore the signal handlers to their previous state (before the
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call to _setup_sig_handler()."""
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signal.signal(signal.SIGINT, self.old_sigint)
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signal.signal(signal.SIGTERM, self.old_sigterm)
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try:
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signal.signal(signal.SIGHUP, self.old_sighup)
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except AttributeError:
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pass
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class Serial:
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"""This class is used to execute tasks in series, and is more efficient
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than Parallel, but is only appropriate for non-parallel builds. Only
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one instance of this class should be in existence at a time.
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This class is not thread safe.
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"""
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def __init__(self, taskmaster):
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"""Create a new serial job given a taskmaster.
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The taskmaster's next_task() method should return the next task
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that needs to be executed, or None if there are no more tasks. The
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taskmaster's executed() method will be called for each task when it
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is successfully executed, or failed() will be called if it failed to
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execute (e.g. execute() raised an exception)."""
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self.taskmaster = taskmaster
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self.interrupted = InterruptState()
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def start(self):
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"""Start the job. This will begin pulling tasks from the taskmaster
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and executing them, and return when there are no more tasks. If a task
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fails to execute (i.e. execute() raises an exception), then the job will
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stop."""
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while True:
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task = self.taskmaster.next_task()
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if task is None:
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break
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try:
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task.prepare()
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if task.needs_execute():
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task.execute()
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except Exception:
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if self.interrupted():
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try:
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raise SCons.Errors.BuildError(
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task.targets[0], errstr=interrupt_msg)
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except:
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task.exception_set()
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else:
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task.exception_set()
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# Let the failed() callback function arrange for the
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# build to stop if that's appropriate.
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task.failed()
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else:
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task.executed()
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task.postprocess()
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self.taskmaster.cleanup()
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# Trap import failure so that everything in the Job module but the
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# Parallel class (and its dependent classes) will work if the interpreter
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# doesn't support threads.
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try:
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import queue
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import threading
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except ImportError:
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pass
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else:
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class Worker(threading.Thread):
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"""A worker thread waits on a task to be posted to its request queue,
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dequeues the task, executes it, and posts a tuple including the task
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and a boolean indicating whether the task executed successfully. """
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def __init__(self, requestQueue, resultsQueue, interrupted):
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threading.Thread.__init__(self)
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self.setDaemon(1)
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self.requestQueue = requestQueue
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self.resultsQueue = resultsQueue
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self.interrupted = interrupted
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self.start()
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def run(self):
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while True:
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task = self.requestQueue.get()
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if task is None:
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# The "None" value is used as a sentinel by
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# ThreadPool.cleanup(). This indicates that there
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# are no more tasks, so we should quit.
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break
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try:
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if self.interrupted():
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raise SCons.Errors.BuildError(
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task.targets[0], errstr=interrupt_msg)
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task.execute()
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except:
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task.exception_set()
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ok = False
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else:
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ok = True
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self.resultsQueue.put((task, ok))
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class ThreadPool:
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"""This class is responsible for spawning and managing worker threads."""
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def __init__(self, num, stack_size, interrupted):
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"""Create the request and reply queues, and 'num' worker threads.
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One must specify the stack size of the worker threads. The
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stack size is specified in kilobytes.
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"""
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self.requestQueue = queue.Queue(0)
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self.resultsQueue = queue.Queue(0)
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try:
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prev_size = threading.stack_size(stack_size*1024)
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except AttributeError as e:
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# Only print a warning if the stack size has been
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# explicitly set.
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if explicit_stack_size is not None:
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msg = "Setting stack size is unsupported by this version of Python:\n " + \
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e.args[0]
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SCons.Warnings.warn(SCons.Warnings.StackSizeWarning, msg)
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except ValueError as e:
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msg = "Setting stack size failed:\n " + str(e)
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SCons.Warnings.warn(SCons.Warnings.StackSizeWarning, msg)
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# Create worker threads
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self.workers = []
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for _ in range(num):
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worker = Worker(self.requestQueue, self.resultsQueue, interrupted)
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self.workers.append(worker)
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if 'prev_size' in locals():
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threading.stack_size(prev_size)
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def put(self, task):
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"""Put task into request queue."""
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self.requestQueue.put(task)
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def get(self):
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"""Remove and return a result tuple from the results queue."""
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return self.resultsQueue.get()
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def preparation_failed(self, task):
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self.resultsQueue.put((task, False))
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def cleanup(self):
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"""
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Shuts down the thread pool, giving each worker thread a
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chance to shut down gracefully.
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"""
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# For each worker thread, put a sentinel "None" value
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# on the requestQueue (indicating that there's no work
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# to be done) so that each worker thread will get one and
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# terminate gracefully.
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for _ in self.workers:
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self.requestQueue.put(None)
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# Wait for all of the workers to terminate.
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#
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# If we don't do this, later Python versions (2.4, 2.5) often
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# seem to raise exceptions during shutdown. This happens
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# in requestQueue.get(), as an assertion failure that
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# requestQueue.not_full is notified while not acquired,
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# seemingly because the main thread has shut down (or is
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# in the process of doing so) while the workers are still
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# trying to pull sentinels off the requestQueue.
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#
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# Normally these terminations should happen fairly quickly,
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# but we'll stick a one-second timeout on here just in case
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# someone gets hung.
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for worker in self.workers:
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worker.join(1.0)
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self.workers = []
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class Parallel:
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"""This class is used to execute tasks in parallel, and is somewhat
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less efficient than Serial, but is appropriate for parallel builds.
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This class is thread safe.
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"""
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def __init__(self, taskmaster, num, stack_size):
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"""Create a new parallel job given a taskmaster.
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The taskmaster's next_task() method should return the next
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task that needs to be executed, or None if there are no more
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tasks. The taskmaster's executed() method will be called
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for each task when it is successfully executed, or failed()
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will be called if the task failed to execute (i.e. execute()
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raised an exception).
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Note: calls to taskmaster are serialized, but calls to
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execute() on distinct tasks are not serialized, because
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that is the whole point of parallel jobs: they can execute
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multiple tasks simultaneously. """
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self.taskmaster = taskmaster
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self.interrupted = InterruptState()
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self.tp = ThreadPool(num, stack_size, self.interrupted)
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self.maxjobs = num
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def start(self):
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"""Start the job. This will begin pulling tasks from the
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taskmaster and executing them, and return when there are no
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more tasks. If a task fails to execute (i.e. execute() raises
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an exception), then the job will stop."""
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jobs = 0
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while True:
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# Start up as many available tasks as we're
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# allowed to.
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while jobs < self.maxjobs:
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task = self.taskmaster.next_task()
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if task is None:
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break
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try:
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# prepare task for execution
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task.prepare()
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except:
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task.exception_set()
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task.failed()
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task.postprocess()
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else:
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if task.needs_execute():
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# dispatch task
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self.tp.put(task)
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jobs = jobs + 1
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else:
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task.executed()
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task.postprocess()
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if not task and not jobs: break
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# Let any/all completed tasks finish up before we go
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# back and put the next batch of tasks on the queue.
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while True:
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task, ok = self.tp.get()
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jobs = jobs - 1
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if ok:
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task.executed()
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else:
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if self.interrupted():
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try:
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raise SCons.Errors.BuildError(
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task.targets[0], errstr=interrupt_msg)
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except:
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task.exception_set()
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# Let the failed() callback function arrange
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# for the build to stop if that's appropriate.
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task.failed()
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task.postprocess()
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if self.tp.resultsQueue.empty():
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break
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self.tp.cleanup()
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self.taskmaster.cleanup()
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# Local Variables:
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# tab-width:4
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# indent-tabs-mode:nil
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# End:
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# vim: set expandtab tabstop=4 shiftwidth=4:
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