我的情况是这样的:我正在为一门操作系统课程编写UNIX|
.我完成了我的实现;然而,我注意到我不确定地通过了测试用例.所讨论的测试用例的形式如下:
def test_no_orphans(self):
self.assertTrue(self.make, msg='make failed')
subprocess.call(('strace', '-o', 'trace.log','./pipe','ls','wc','cat','cat'))
ps = subprocess.Popen(['grep','-o','clone(','trace.log'], stdout=subprocess.PIPE)
out1 = subprocess.check_output(('wc','-l'), stdin=ps.stdout)
ps.wait()
ps.stdout.close()
ps = subprocess.Popen(['grep','-o','wait','trace.log'], stdout=subprocess.PIPE)
out2 = subprocess.check_output(('wc','-l'), stdin=ps.stdout)
ps.wait()
ps.stdout.close()
out1 = int(out1.decode("utf-8")[0])
out2 = int(out2.decode("utf-8")[0])
if out1 == out2 or out1 < out2:
orphan_check = True
else:
orphan_check = False
self.assertTrue(orphan_check, msg="Found orphan processes")
subprocess.call(['rm', 'trace.log'])
self.assertTrue(self._make_clean, msg='make clean failed')
在查阅有关日志(log)后,我发现:
clone(child_stack=NULL, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7f04174ad850) = 1330
close(4) = 0
--- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=1330, si_uid=1000, si_status=0, si_utime=0, si_stime=0} ---
pipe([4, 5]) = 0
clone(child_stack=NULL, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7f04174ad850) = 1331
close(5) = 0
close(3) = 0
pipe([3, 5]) = 0
clone(child_stack=NULL, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7f04174ad850) = ? ERESTARTNOINTR (To be restarted)
--- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=1331, si_uid=1000, si_status=0, si_utime=0, si_stime=0} ---
clone(child_stack=NULL, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7f04174ad850) = 1332
close(5) = 0
--- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=1332, si_uid=1000, si_status=0, si_utime=0, si_stime=0} ---
close(4) = 0
pipe([4, 5]) = 0
clone(child_stack=NULL, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7f04174ad850) = 1333
具体地说,排在ERESTARTNOINTR (To be restarted)
位的队伍让我失败了.在我的教授帮助我调试后,我向负责这项任务的助教报告了这一点,并说这可能是测试用例中的错误.
我想知道为什么正好clone()
会失败,因为fork()
似乎用一个很好的C包装器为我们处理了这个问题.我还想知道这里到底发生了什么,还有为什么系统调用似乎总体上似乎有incomplete
和resumed
的状态,因为我的操作系统教授说他对此了解不多,他基本上说这可能是"内核中的竞争条件".