Added an unmodified copy of SCons to third_party.

scons-2.0.1/engine/SCons/Job.py

+"""SCons.Job
+
+This module defines the Serial and Parallel classes that execute tasks to
+complete a build. The Jobs class provides a higher level interface to start,
+stop, and wait on jobs.
+
+"""
+
+#
+# Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 The SCons Foundation
+#
+# Permission is hereby granted, free of charge, to any person obtaining
+# a copy of this software and associated documentation files (the
+# "Software"), to deal in the Software without restriction, including
+# without limitation the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the Software, and to
+# permit persons to whom the Software is furnished to do so, subject to
+# the following conditions:
+#
+# The above copyright notice and this permission notice shall be included
+# in all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
+# KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
+# WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+#
+
+__revision__ = "src/engine/SCons/Job.py 5134 2010/08/16 23:02:40 bdeegan"
+
+import SCons.compat
+
+import os
+import signal
+
+import SCons.Errors
+
+# The default stack size (in kilobytes) of the threads used to execute
+# jobs in parallel.
+#
+# We use a stack size of 256 kilobytes. The default on some platforms
+# is too large and prevents us from creating enough threads to fully
+# parallelized the build. For example, the default stack size on linux
+# is 8 MBytes.
+
+explicit_stack_size = None
+default_stack_size = 256
+
+interrupt_msg = 'Build interrupted.'
+
+
+class InterruptState(object):
+   def __init__(self):
+       self.interrupted = False
+
+   def set(self):
+       self.interrupted = True
+
+   def __call__(self):
+       return self.interrupted
+
+
+class Jobs(object):
+    """An instance of this class initializes N jobs, and provides
+    methods for starting, stopping, and waiting on all N jobs.
+    """
+
+    def __init__(self, num, taskmaster):
+        """
+        create 'num' jobs using the given taskmaster.
+
+        If 'num' is 1 or less, then a serial job will be used,
+        otherwise a parallel job with 'num' worker threads will
+        be used.
+
+        The 'num_jobs' attribute will be set to the actual number of jobs
+        allocated.  If more than one job is requested but the Parallel
+        class can't do it, it gets reset to 1.  Wrapping interfaces that
+        care should check the value of 'num_jobs' after initialization.
+        """
+
+        self.job = None
+        if num > 1:
+            stack_size = explicit_stack_size
+            if stack_size is None:
+                stack_size = default_stack_size
+                
+            try:
+                self.job = Parallel(taskmaster, num, stack_size)
+                self.num_jobs = num
+            except NameError:
+                pass
+        if self.job is None:
+            self.job = Serial(taskmaster)
+            self.num_jobs = 1
+
+    def run(self, postfunc=lambda: None):
+        """Run the jobs.
+
+        postfunc() will be invoked after the jobs has run. It will be
+        invoked even if the jobs are interrupted by a keyboard
+        interrupt (well, in fact by a signal such as either SIGINT,
+        SIGTERM or SIGHUP). The execution of postfunc() is protected
+        against keyboard interrupts and is guaranteed to run to
+        completion."""
+        self._setup_sig_handler()
+        try:
+            self.job.start()
+        finally:
+            postfunc()
+            self._reset_sig_handler()
+
+    def were_interrupted(self):
+        """Returns whether the jobs were interrupted by a signal."""
+        return self.job.interrupted()
+
+    def _setup_sig_handler(self):
+        """Setup an interrupt handler so that SCons can shutdown cleanly in
+        various conditions:
+
+          a) SIGINT: Keyboard interrupt
+          b) SIGTERM: kill or system shutdown
+          c) SIGHUP: Controlling shell exiting
+
+        We handle all of these cases by stopping the taskmaster. It
+        turns out that it very difficult to stop the build process
+        by throwing asynchronously an exception such as
+        KeyboardInterrupt. For example, the python Condition
+        variables (threading.Condition) and queue's do not seem to
+        asynchronous-exception-safe. It would require adding a whole
+        bunch of try/finally block and except KeyboardInterrupt all
+        over the place.
+
+        Note also that we have to be careful to handle the case when
+        SCons forks before executing another process. In that case, we
+        want the child to exit immediately.
+        """
+        def handler(signum, stack, self=self, parentpid=os.getpid()):
+            if os.getpid() == parentpid:
+                self.job.taskmaster.stop()
+                self.job.interrupted.set()
+            else:
+                os._exit(2)
+
+        self.old_sigint  = signal.signal(signal.SIGINT, handler)
+        self.old_sigterm = signal.signal(signal.SIGTERM, handler)
+        try:
+            self.old_sighup = signal.signal(signal.SIGHUP, handler)
+        except AttributeError:
+            pass
+
+    def _reset_sig_handler(self):
+        """Restore the signal handlers to their previous state (before the
+         call to _setup_sig_handler()."""
+
+        signal.signal(signal.SIGINT, self.old_sigint)
+        signal.signal(signal.SIGTERM, self.old_sigterm)
+        try:
+            signal.signal(signal.SIGHUP, self.old_sighup)
+        except AttributeError:
+            pass
+
+class Serial(object):
+    """This class is used to execute tasks in series, and is more efficient
+    than Parallel, but is only appropriate for non-parallel builds. Only
+    one instance of this class should be in existence at a time.
+
+    This class is not thread safe.
+    """
+
+    def __init__(self, taskmaster):
+        """Create a new serial job given a taskmaster. 
+
+        The taskmaster's next_task() method should return the next task
+        that needs to be executed, or None if there are no more tasks. The
+        taskmaster's executed() method will be called for each task when it
+        is successfully executed or failed() will be called if it failed to
+        execute (e.g. execute() raised an exception)."""
+        
+        self.taskmaster = taskmaster
+        self.interrupted = InterruptState()
+
+    def start(self):
+        """Start the job. This will begin pulling tasks from the taskmaster
+        and executing them, and return when there are no more tasks. If a task
+        fails to execute (i.e. execute() raises an exception), then the job will
+        stop."""
+        
+        while True:
+            task = self.taskmaster.next_task()
+
+            if task is None:
+                break
+
+            try:
+                task.prepare()
+                if task.needs_execute():
+                    task.execute()
+            except:
+                if self.interrupted():
+                    try:
+                        raise SCons.Errors.BuildError(
+                            task.targets[0], errstr=interrupt_msg)
+                    except:
+                        task.exception_set()
+                else:
+                    task.exception_set()
+
+                # Let the failed() callback function arrange for the
+                # build to stop if that's appropriate.
+                task.failed()
+            else:
+                task.executed()
+
+            task.postprocess()
+        self.taskmaster.cleanup()
+
+
+# Trap import failure so that everything in the Job module but the
+# Parallel class (and its dependent classes) will work if the interpreter
+# doesn't support threads.
+try:
+    import queue
+    import threading
+except ImportError:
+    pass
+else:
+    class Worker(threading.Thread):
+        """A worker thread waits on a task to be posted to its request queue,
+        dequeues the task, executes it, and posts a tuple including the task
+        and a boolean indicating whether the task executed successfully. """
+
+        def __init__(self, requestQueue, resultsQueue, interrupted):
+            threading.Thread.__init__(self)
+            self.setDaemon(1)
+            self.requestQueue = requestQueue
+            self.resultsQueue = resultsQueue
+            self.interrupted = interrupted
+            self.start()
+
+        def run(self):
+            while True:
+                task = self.requestQueue.get()
+
+                if task is None:
+                    # The "None" value is used as a sentinel by
+                    # ThreadPool.cleanup().  This indicates that there
+                    # are no more tasks, so we should quit.
+                    break
+
+                try:
+                    if self.interrupted():
+                        raise SCons.Errors.BuildError(
+                            task.targets[0], errstr=interrupt_msg)
+                    task.execute()
+                except:
+                    task.exception_set()
+                    ok = False
+                else:
+                    ok = True
+
+                self.resultsQueue.put((task, ok))
+
+    class ThreadPool(object):
+        """This class is responsible for spawning and managing worker threads."""
+
+        def __init__(self, num, stack_size, interrupted):
+            """Create the request and reply queues, and 'num' worker threads.
+            
+            One must specify the stack size of the worker threads. The
+            stack size is specified in kilobytes.
+            """
+            self.requestQueue = queue.Queue(0)
+            self.resultsQueue = queue.Queue(0)
+
+            try:
+                prev_size = threading.stack_size(stack_size*1024) 
+            except AttributeError, e:
+                # Only print a warning if the stack size has been
+                # explicitly set.
+                if not explicit_stack_size is None:
+                    msg = "Setting stack size is unsupported by this version of Python:\n    " + \
+                        e.args[0]
+                    SCons.Warnings.warn(SCons.Warnings.StackSizeWarning, msg)
+            except ValueError, e:
+                msg = "Setting stack size failed:\n    " + str(e)
+                SCons.Warnings.warn(SCons.Warnings.StackSizeWarning, msg)
+
+            # Create worker threads
+            self.workers = []
+            for _ in range(num):
+                worker = Worker(self.requestQueue, self.resultsQueue, interrupted)
+                self.workers.append(worker)
+
+            if 'prev_size' in locals():
+                threading.stack_size(prev_size)
+
+        def put(self, task):
+            """Put task into request queue."""
+            self.requestQueue.put(task)
+
+        def get(self):
+            """Remove and return a result tuple from the results queue."""
+            return self.resultsQueue.get()
+
+        def preparation_failed(self, task):
+            self.resultsQueue.put((task, False))
+
+        def cleanup(self):
+            """
+            Shuts down the thread pool, giving each worker thread a
+            chance to shut down gracefully.
+            """
+            # For each worker thread, put a sentinel "None" value
+            # on the requestQueue (indicating that there's no work
+            # to be done) so that each worker thread will get one and
+            # terminate gracefully.
+            for _ in self.workers:
+                self.requestQueue.put(None)
+
+            # Wait for all of the workers to terminate.
+            # 
+            # If we don't do this, later Python versions (2.4, 2.5) often
+            # seem to raise exceptions during shutdown.  This happens
+            # in requestQueue.get(), as an assertion failure that
+            # requestQueue.not_full is notified while not acquired,
+            # seemingly because the main thread has shut down (or is
+            # in the process of doing so) while the workers are still
+            # trying to pull sentinels off the requestQueue.
+            #
+            # Normally these terminations should happen fairly quickly,
+            # but we'll stick a one-second timeout on here just in case
+            # someone gets hung.
+            for worker in self.workers:
+                worker.join(1.0)
+            self.workers = []
+
+    class Parallel(object):
+        """This class is used to execute tasks in parallel, and is somewhat 
+        less efficient than Serial, but is appropriate for parallel builds.
+
+        This class is thread safe.
+        """
+
+        def __init__(self, taskmaster, num, stack_size):
+            """Create a new parallel job given a taskmaster.
+
+            The taskmaster's next_task() method should return the next
+            task that needs to be executed, or None if there are no more
+            tasks. The taskmaster's executed() method will be called
+            for each task when it is successfully executed or failed()
+            will be called if the task failed to execute (i.e. execute()
+            raised an exception).
+
+            Note: calls to taskmaster are serialized, but calls to
+            execute() on distinct tasks are not serialized, because
+            that is the whole point of parallel jobs: they can execute
+            multiple tasks simultaneously. """
+
+            self.taskmaster = taskmaster
+            self.interrupted = InterruptState()
+            self.tp = ThreadPool(num, stack_size, self.interrupted)
+
+            self.maxjobs = num
+
+        def start(self):
+            """Start the job. This will begin pulling tasks from the
+            taskmaster and executing them, and return when there are no
+            more tasks. If a task fails to execute (i.e. execute() raises
+            an exception), then the job will stop."""
+
+            jobs = 0
+            
+            while True:
+                # Start up as many available tasks as we're
+                # allowed to.
+                while jobs < self.maxjobs:
+                    task = self.taskmaster.next_task()
+                    if task is None:
+                        break
+
+                    try:
+                        # prepare task for execution
+                        task.prepare()
+                    except:
+                        task.exception_set()
+                        task.failed()
+                        task.postprocess()
+                    else:
+                        if task.needs_execute():
+                            # dispatch task
+                            self.tp.put(task)
+                            jobs = jobs + 1
+                        else:
+                            task.executed()
+                            task.postprocess()
+
+                if not task and not jobs: break
+
+                # Let any/all completed tasks finish up before we go
+                # back and put the next batch of tasks on the queue.
+                while True:
+                    task, ok = self.tp.get()
+                    jobs = jobs - 1
+
+                    if ok:
+                        task.executed()
+                    else:
+                        if self.interrupted():
+                            try:
+                                raise SCons.Errors.BuildError(
+                                    task.targets[0], errstr=interrupt_msg)
+                            except:
+                                task.exception_set()
+
+                        # Let the failed() callback function arrange
+                        # for the build to stop if that's appropriate.
+                        task.failed()
+
+                    task.postprocess()
+
+                    if self.tp.resultsQueue.empty():
+                        break
+
+            self.tp.cleanup()
+            self.taskmaster.cleanup()
+
+# Local Variables:
+# tab-width:4
+# indent-tabs-mode:nil
+# End:
+# vim: set expandtab tabstop=4 shiftwidth=4: