父子进程 signal 出现 Interrupted system call 问题
这里我有三个进程,
一个是主进程, 先是 fork 一个子进程 ppid
然后 ppid 又 fork一个子进程 pid
目的是让 ppid 来启动 pid, 并负责 pid 的正常运行(例如 pid 如果退出了,可以让 ppid 来重新启动它)
但是我想要在主进程中利用一个信号来结束这个进程(pid), 然后ppid 得到 waitpid(pid, 0) 的返回值,最终整个分支进程全部退出.
代码如下:
import os
import time
import signal
def my_fork():
ppid = os.fork()
if ppid == 0:
pid = os.fork()
if pid == 0:
global n
n = 1
def handler(signum, frame):
print "Catch the signal %s" % signum
global n
n = 0
signal.signal(signal.SIGUSR1, handler)
print "The p child %s" % os.getpid()
# run the logger progream
while 1:
if n:
print "sleeping..."
else:
print "EXIT..................."
break
time.sleep(1)
os._exit(n)
def handler(signum, frame):
os.kill( pid, signum)
signal.signal(signal.SIGUSR1, handler)
print "The pp child %s" % os.getpid()
status = 1
try:
status = os.waitpid(pid, 0)[1] # 代码[1]
except OSError,e:
if e.errno == 4:
print "###########%s %s"%(pid, id(pid))
print str(e)
if status == 0:
print "The pid %s exit normally" % pid
os._exit(status)
else:
time.sleep(3)
os.kill(ppid, signal.SIGUSR1)
os.waitpid(ppid, 0)
if __name__ == "__main__":
my_fork()
遇到一问题, 如果代码[1]处不加 try except处理,则会得到一个 OSError
The p child 6555
sleeping...
The pp child 6554
sleeping...
sleeping...
Traceback (most recent call last):
File "fork1.py", line 45, in <module>
my_fork()
File "fork1.py", line 35, in my_fork
status = os.waitpid(pid, 0)[1]
OSError: [Errno 4] Interrupted system call
Catch the signal 10
EXIT...................
google了半天也没有解决问题,最终还是用 try except 来处理的. 因为发现别人也是这么处理的...
http://marc.info/?l=zodb-checkins&m=106930249605396&w=1
+ raise KidDiedOnMeError + except OSError, num: + if num == 4: + # This is likely an interrupted system call + # inside os.waitpid caused by a signal. + # Though we have to catch it, we don't really + # care about it and we just pass. + pass