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waf/playground/maxjobs/wscript
2011-12-09 21:24:07 +01:00

66 lines
1.7 KiB
Python

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