Question

我正在开发一个应该检查计算机是否能够ping google.com的应用程序。为此，我使用python子进程模块并发出一个调用，如下面的代码所示：

response = subprocess.call("ping -c 1 google.com -q", shell=True)

然而，在运行一段时间后，程序退出并出现分段错误。

我有以下代码：

daemon.py

def dataset_save(smartphone, mote):
print("DATA LOGGER:\tStarting Now")
with open('dataset.csv', 'a+') as dataset:
    dataset.write(str(datetime.datetime.today()) + ',' + \
            str(datetime.datetime.today().weekday()) + ',' + \
            str(smartphone.connected) + ',' + \
            str(mote.A0_pw) + ',' + \
            str(mote.B00_pw) + ',' + \
            str(mote.B01_pw) + ',' + \
            str(mote.B10_pw) + ',' + \
            str(mote.B11_pw) + ',' + \
            str(presence.get_value()) + ',' + \
            str(temperature.get_value()) + ',' + \
            str(luminosity.get_value()) + '\n')
    print("DATA LOGGER: \tData successfully logged @ %s!" %str(datetime.datetime.today()))
return


def run():
    check_internet()
    while True:
        dataset_save(smartphone, gateway)
        check_presence()

check_internet.py

def check_internet():
response = subprocess.call("ping -c 1 google.com -q", shell=True)
print(response)
if response == 0:
    print ("CONNECTIVITY: \tConnected to internet")
    threading.Timer(1, check_internet).start()
    return

else: 
    print("CONNECTIVITY: \tUnable to connect to internet")
    threading.Timer(1, check_internet).start()
    return

在GDB上运行我在分段错误时得到以下跟踪：

--- google.com ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 146.626/146.626/146.626/0.000 ms
0
CONNECTIVITY:   Connected to internet
[New Thread 0xb55ffb40 (LWP 4064)]

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0xb65ffb40 (LWP 4043)]
PING google.com (216.58.222.110) 56(84) bytes of data.
__deallocate_stack (pd=0xb65ffb40) at allocatestack.c:760
760 allocatestack.c: No such file or directory.
(gdb) 
--- google.com ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 146.504/146.504/146.504/0.000 ms

(gdb) bt
#0  __deallocate_stack (pd=0xb65ffb40) at allocatestack.c:760
#1  0xb7fc3eab in start_thread (arg=0xb65ffb40) at pthread_create.c:427
#2  0xb7e8164e in clone () at ../sysdeps/unix/sysv/linux/i386/clone.S:129
(gdb)

我有什么理由不使用threding.Timer就像我在使用？在我看来，连续创建线程是造成这种分段错误的原因。

感谢。

Answer 1

你正在计时器本身内重新启动计时器，这可能不太好（用线程递归调用，argh）。如果你对ping延迟准确性要求不高，你真的不需要Timer：你可以像这样开始一个循环和ping谷歌的线程：

import threading,subprocess,time

def check_internet():
    while True:
        time.sleep(1)
        response = subprocess.call("ping -n 1 google.com".split())
        print(response)
        if response == 0:
            print("CONNECTIVITY: \tConnected to internet")
        else:
            print("CONNECTIVITY: \tUnable to connect to internet")

t=threading.Thread(target=check_internet)
t.start()

print("Started")
t.join()

你只创建1个线程，每1秒创建一个ping进程（它不是一个受监管的计时器，但它应该足够了。）

编辑：没有ping输出的版本：

import threading,subprocess,time

def check_internet():
    while True:
        time.sleep(1)
        p = subprocess.Popen("ping -n 1 google.com".split(),stdout=subprocess.PIPE,stderr=subprocess.STDOUT)
        out,err = p.communicate()
        response = p.wait()
        if response == 0:
            print("CONNECTIVITY: \tConnected to internet")
        else:
            print("CONNECTIVITY: \tUnable to connect to internet")

t=threading.Thread(target=check_internet)
t.start()

print("Started")
t.join()

线程切换上的Python分段错误

1 个答案: