mirror of https://gitlab.com/ita1024/waf.git
66 lines
1.7 KiB
Python
66 lines
1.7 KiB
Python
#! /usr/bin/env python
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# the Task class attribute "maxjobs" was deprecated in Waf 1.6
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# limiting the amount of jobs is commonly done by adding sequential
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# barriers (build groups) or even locks. But the feature might be
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# necessary in very few corner cases
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# in the following examples, remember that the method run() is the only
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# one actually executed by threads
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def configure(conf):
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pass
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def build(bld):
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bld.jobs = 4
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bld(source='foo.a bar.a truc.a')
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import threading, time
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from waflib.TaskGen import extension
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from waflib import Task
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@extension('.a')
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def process_a_files(self, node):
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self.create_task('a_to_b', node, node.change_ext('b'))
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self.create_task('b_to_c', node.change_ext('b'), node.change_ext('c'))
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class a_to_b(Task.Task):
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# classical way, using a lock or a semaphore
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# in this case, at most 2 tasks can execute at a time
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# this may lead to build starvation, as may tasks can get stalled while processing
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lock = threading.Semaphore(2)
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def run(self):
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try:
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self.lock.acquire()
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for i in range(5):
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print('a to b %r' % id(self))
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time.sleep(1)
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self.outputs[0].write('done')
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finally:
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self.lock.release()
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class b_to_c(Task.Task):
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# this will enable other tasks to run concurrently, and without additional locks
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active = []
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def runnable_status(self):
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ret = Task.Task.runnable_status(self)
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if ret == Task.RUN_ME:
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self.active = [tsk for tsk in self.active if not tsk.hasrun]
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if len(self.active) < 2:
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self.active.append(self)
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else:
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# too many tasks are still active, wait
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ret = Task.ASK_LATER
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return ret
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def run(self):
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for i in range(5):
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print('b to c %r' % id(self))
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time.sleep(1)
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self.outputs[0].write('done')
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