用 GDB 排查 Python 程序故障_程序人生

用 GDB 排查 Python 程序故障

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2023-07-30 21:56:23

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某Team在用Python开发一些代码，涉及子进程以及设法消除僵尸进程的需求。实践中他们碰上Python程序非预期退出的现象。最初他们决定用GDB调试Python解释器，查看exit()的源头。我听了之后，觉得这个问题应该用别的调试思路。帮他们排查这次程序故障时，除去原始问题，还衍生了其他问题。
这次的问题相比西安研发中心曾经碰上的Python信号处理问题，有不少基础知识、先验知识是共用的，此处不做再普及，感兴趣的同学可以翻看我以前发过的文章。

下文是一次具体的调试、分析记录。为了简化现场、方便调试，已将原始问题、衍生问题浓缩成DebugPythonWithGDB_6.py、DebugPythonWithGDB_7.py。

$ vi DebugPythonWithGDB_6.py

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#!/usr/bin/env python# -*- encoding: utf-8 -*-?import sys, os, signal, subprocess, shlex, traceback?def on_SIGCHLD ( signum, frame ) :????print \”[on_SIGCHLD\”????sys.stdout.write( \”signum??= %u\\n\” % signum )????traceback.print_stack( frame )????print os.waitpid( –1, os.WNOHANG )????\”\”\”????try :????????print os.waitpid( -1, os.WNOHANG )????except OSError :????????sys.stdout.write( \’Line[%u]: OSError\\n\’ % sys.exc_info()[2].tb_lineno )????\”\”\”????print \”on_SIGCHLD]\”?def do_more ( count ) :????print \'[do_more() begin %u]\’ % count????os.system( r\’printf \”Child?? = %u\\n\” \” />;/bin/sleep 1\’ ) \”\”\” # # 这里存在竞争条件，可以增加触发OSError异常的概率 # os.system( r\’printf \”Child = %u\\n\”

os.system( r\’printf \”Child = %u\\n\”

\”\”\” print \'[do_more() end %u]\’ % count def main ( prog, args ) : if 0 == len( args ) : print \’Usage: %s \’ % prog else : sys.stdout.write( \”Parent = %u\\n\” % os.getpid() ) # # 本例中，即使有下列代码，Ctrl-C仍然无效。 # signal.signal( signal.SIGINT, signal.SIG_DFL ) # # signal.signal( signal.SIGCHLD, signal.SIG_IGN ) # signal.signal( signal.SIGCHLD, on_SIGCHLD ) # count = 0 while True : # # 本例中父进程只是一个调度框架，不需要与子进程进行通信，因此不 # 需要特别处理\”stdin=None, stdout=None, stderr=None\”。 # child = subprocess.Popen \\ ( # # 不要直接用args[0].split()，它在处理单、双引号时不是我们 # 期望的行为。考虑这种例子，ls -l \”/tmp/non exist\” # shlex.split( args[0] ), # # all file descriptors except 0, 1 and 2 will be closed # before the child process is executed # close_fds = True, cwd = \”/tmp\” ) sys.stdout.write( \”Child = %u\\n\” % child.pid ) # # child.send_signal( signal.SIGTERM ) # child.terminate() # child.kill() # # child.wait() # do_more( count ) count += 1 if \’__main__\’ == __name__ : try : main( os.path.basename( sys.argv[0] ), sys.argv[1:] ) except KeyboardInterrupt : pass

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$ python DebugPythonWithGDB_6.py \’python -c \”import time;time.sleep(3600)\”\’Parent = 10244Child = 10245[do_more() begin 0][on_SIGCHLDsignum = 17 File \”DebugPythonWithGDB_6.py\”, line 81, in main( os.path.basename( sys.argv[0] ), sys.argv[1:] ) File \”DebugPythonWithGDB_6.py\”, line 76, in main do_more( count ) File \”DebugPythonWithGDB_6.py\”, line 20, in do_more print \'[do_more() begin %u]\’ % count(10245, 9)on_SIGCHLD]Child = 10246[on_SIGCHLDsignum = 17 File \”DebugPythonWithGDB_6.py\”, line 81, in main( os.path.basename( sys.argv[0] ), sys.argv[1:] ) File \”DebugPythonWithGDB_6.py\”, line 76, in main do_more( count ) File \”DebugPythonWithGDB_6.py\”, line 21, in do_more

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用 GDB 排查 Python 程序故障

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