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Diffstat (limited to 'js/src/gdb/taskpool.py')
| -rw-r--r-- | js/src/gdb/taskpool.py | 240 |
1 files changed, 240 insertions, 0 deletions
diff --git a/js/src/gdb/taskpool.py b/js/src/gdb/taskpool.py new file mode 100644 index 0000000000..38254af6b3 --- /dev/null +++ b/js/src/gdb/taskpool.py @@ -0,0 +1,240 @@ +# This Source Code Form is subject to the terms of the Mozilla Public +# License, v. 2.0. If a copy of the MPL was not distributed with this file, +# You can obtain one at http://mozilla.org/MPL/2.0/. + +# flake8: noqa: F821 + +import fcntl +import os +import select +import time +from subprocess import PIPE, Popen + + +class TaskPool(object): + # Run a series of subprocesses. Try to keep up to a certain number going in + # parallel at any given time. Enforce time limits. + # + # This is implemented using non-blocking I/O, and so is Unix-specific. + # + # We assume that, if a task closes its standard error, then it's safe to + # wait for it to terminate. So an ill-behaved task that closes its standard + # output and then hangs will hang us, as well. However, as it takes special + # effort to close one's standard output, this seems unlikely to be a + # problem in practice. + + # A task we should run in a subprocess. Users should subclass this and + # fill in the methods as given. + class Task(object): + def __init__(self): + self.pipe = None + self.start_time = None + + # Record that this task is running, with |pipe| as its Popen object, + # and should time out at |deadline|. + def start(self, pipe, deadline): + self.pipe = pipe + self.deadline = deadline + + # Return a shell command (a string or sequence of arguments) to be + # passed to Popen to run the task. The command will be given + # /dev/null as its standard input, and pipes as its standard output + # and error. + def cmd(self): + raise NotImplementedError + + # TaskPool calls this method to report that the process wrote + # |string| to its standard output. + def onStdout(self, string): + raise NotImplementedError + + # TaskPool calls this method to report that the process wrote + # |string| to its standard error. + def onStderr(self, string): + raise NotImplementedError + + # TaskPool calls this method to report that the process terminated, + # yielding |returncode|. + def onFinished(self, returncode): + raise NotImplementedError + + # TaskPool calls this method to report that the process timed out and + # was killed. + def onTimeout(self): + raise NotImplementedError + + # If a task output handler (onStdout, onStderr) throws this, we terminate + # the task. + class TerminateTask(Exception): + pass + + def __init__(self, tasks, cwd=".", job_limit=4, timeout=150): + self.pending = iter(tasks) + self.cwd = cwd + self.job_limit = job_limit + self.timeout = timeout + self.next_pending = next(self.pending, None) + + def run_all(self): + # The currently running tasks: a set of Task instances. + running = set() + with open(os.devnull, "r") as devnull: + while True: + while len(running) < self.job_limit and self.next_pending: + task = self.next_pending + p = Popen( + task.cmd(), + bufsize=16384, + stdin=devnull, + stdout=PIPE, + stderr=PIPE, + cwd=self.cwd, + ) + + # Put the stdout and stderr pipes in non-blocking mode. See + # the post-'select' code below for details. + flags = fcntl.fcntl(p.stdout, fcntl.F_GETFL) + fcntl.fcntl(p.stdout, fcntl.F_SETFL, flags | os.O_NONBLOCK) + flags = fcntl.fcntl(p.stderr, fcntl.F_GETFL) + fcntl.fcntl(p.stderr, fcntl.F_SETFL, flags | os.O_NONBLOCK) + + task.start(p, time.time() + self.timeout) + running.add(task) + self.next_pending = next(self.pending, None) + + # If we have no tasks running, and the above wasn't able to + # start any new ones, then we must be done! + if not running: + break + + # How many seconds do we have until the earliest deadline? + now = time.time() + secs_to_next_deadline = max(min([t.deadline for t in running]) - now, 0) + + # Wait for output or a timeout. + stdouts_and_stderrs = [t.pipe.stdout for t in running] + [ + t.pipe.stderr for t in running + ] + (readable, w, x) = select.select( + stdouts_and_stderrs, [], [], secs_to_next_deadline + ) + finished = set() + terminate = set() + for t in running: + # Since we've placed the pipes in non-blocking mode, these + # 'read's will simply return as many bytes as are available, + # rather than blocking until they have accumulated the full + # amount requested (or reached EOF). The 'read's should + # never throw, since 'select' has told us there was + # something available. + if t.pipe.stdout in readable: + output = t.pipe.stdout.read(16384) + if len(output): + try: + t.onStdout(output.decode("utf-8")) + except TerminateTask: + terminate.add(t) + if t.pipe.stderr in readable: + output = t.pipe.stderr.read(16384) + if len(output): + try: + t.onStderr(output.decode("utf-8")) + except TerminateTask: + terminate.add(t) + else: + # We assume that, once a task has closed its stderr, + # it will soon terminate. If a task closes its + # stderr and then hangs, we'll hang too, here. + t.pipe.wait() + t.onFinished(t.pipe.returncode) + finished.add(t) + # Remove the finished tasks from the running set. (Do this here + # to avoid mutating the set while iterating over it.) + running -= finished + + # Terminate any tasks whose handlers have asked us to do so. + for t in terminate: + t.pipe.terminate() + t.pipe.wait() + running.remove(t) + + # Terminate any tasks which have missed their deadline. + finished = set() + for t in running: + if now >= t.deadline: + t.pipe.terminate() + t.pipe.wait() + t.onTimeout() + finished.add(t) + # Remove the finished tasks from the running set. (Do this here + # to avoid mutating the set while iterating over it.) + running -= finished + return None + + +def get_cpu_count(): + """ + Guess at a reasonable parallelism count to set as the default for the + current machine and run. + """ + # Python 2.6+ + try: + import multiprocessing + + return multiprocessing.cpu_count() + except (ImportError, NotImplementedError): + pass + + # POSIX + try: + res = int(os.sysconf("SC_NPROCESSORS_ONLN")) + if res > 0: + return res + except (AttributeError, ValueError): + pass + + # Windows + try: + res = int(os.environ["NUMBER_OF_PROCESSORS"]) + if res > 0: + return res + except (KeyError, ValueError): + pass + + return 1 + + +if __name__ == "__main__": + # Test TaskPool by using it to implement the unique 'sleep sort' algorithm. + def sleep_sort(ns, timeout): + sorted = [] + + class SortableTask(TaskPool.Task): + def __init__(self, n): + super(SortableTask, self).__init__() + self.n = n + + def start(self, pipe, deadline): + super(SortableTask, self).start(pipe, deadline) + + def cmd(self): + return ["sh", "-c", "echo out; sleep %d; echo err>&2" % (self.n,)] + + def onStdout(self, text): + print("%d stdout: %r" % (self.n, text)) + + def onStderr(self, text): + print("%d stderr: %r" % (self.n, text)) + + def onFinished(self, returncode): + print("%d (rc=%d)" % (self.n, returncode)) + sorted.append(self.n) + + def onTimeout(self): + print("%d timed out" % (self.n,)) + + p = TaskPool([SortableTask(_) for _ in ns], job_limit=len(ns), timeout=timeout) + p.run_all() + return sorted + + print(repr(sleep_sort([1, 1, 2, 3, 5, 8, 13, 21, 34], 15))) |