假设一个服务器上运行了下面这样的 test.py 程序，我们怎样才能知道程序是否在正常运行，运行到哪一步了呢？
import time def do(x): time.sleep(10) def main(): for x in range(10000): do(x) if __name__ == '__main__': main()
这个程序既没有日志也没有 print 输出，通过查看日志文件/标准输出/标准错误是没有办法确认程序状况的。 一种可行的办法就是使用 gdb 来查看程序当前的运行状况。
测试环境¶
- 系统: Ubuntu 16.04.1 LTS
- Python: 2.7.12
准备工作¶
安装 gdb 和 python2.7-dbg:
$ sudo apt-get install gdb python2.7-dbg
设置 /proc/sys/kernel/yama/ptrace_scope:
$ echo 0 |sudo tee /proc/sys/kernel/yama/ptrace_scope
运行 test.py:
$ python test.py & [1] 6489
通过 gdb python PID 来调试运行中的进程:
$ gdb python 6489 GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.04) 7.11.1 ... For help, type "help". Type "apropos word" to search for commands related to "word"... Reading symbols from python...Reading symbols from /usr/lib/debug/.build-id/90/d1300febaeb0a626baa2540d19df2416cd3361.debug...done. done. ... Reading symbols from /lib/ld-linux.so.2...Reading symbols from /usr/lib/debug//lib/i386-linux-gnu/ld-2.23.so...done. done. 0xb778fc31 in __kernel_vsyscall () (gdb)
生成 core file¶
为了不影响运行中的进程，可以通过生成 core file 的方式来保存进程的当前信息:
(gdb) generate-core-file warning: target file /proc/6489/cmdline contained unexpected null characters Saved corefile core.6489 (gdb) quit A debugging session is active. Inferior 1 [process 6489] will be detached. Quit anyway? (y or n) y
可以通过 gdb python core.PID 的方式来读取 core file:
$ gdb python core.6489 GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.04) 7.11.1 ... Type "apropos word" to search for commands related to "word"... Reading symbols from python...Reading symbols from /usr/lib/debug/.build-id/90/d1300febaeb0a626baa2540d19df2416cd3361.debug...done. done. warning: core file may not match specified executable file. [New LWP 6489] [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib/i386-linux-gnu/libthread_db.so.1". Core was generated by `python'. #0 0xb778fc31 in __kernel_vsyscall () (gdb)
可用的 python 相关的命令¶
可以通过输入 py 然后加 tab 键的方式来查看可用的命令:
(gdb) py py-bt py-down py-locals py-up python-interactive py-bt-full py-list py-print python
可以通过 help cmd 查看各个命令的说明:
(gdb) help py-bt Display the current python frame and all the frames within its call stack (if any)
当前执行位置的源码¶
(gdb) py-list 1 # -*- coding: utf-8 -*- 2 import time 3 4 5 def do(x): >6 time.sleep(10) 7 8 9 def main(): 10 for x in range(10000): 11 do(x) (gdb)
可以看到当前正在执行 time.sleep(10)
当前位置的调用栈¶
(gdb) py-bt Traceback (most recent call first): <built-in function sleep> File "test.py", line 6, in do time.sleep(10) File "test.py", line 11, in main do(x) File "test.py", line 15, in <module> main() (gdb)
可以看出来是 main() -> do(x) -> time.sleep(10)
查看变量的值¶
(gdb) py-list 1 # -*- coding: utf-8 -*- 2 import time 3 4 5 def do(x): >6 time.sleep(10) 7 8 9 def main(): 10 for x in range(10000): 11 do(x) (gdb) py-print x local 'x' = 12 (gdb) (gdb) py-locals x = 12 (gdb)
查看上层调用方的信息¶
(gdb) py-up #9 Frame 0xb74c0994, for file test.py, line 11, in main (x=12) do(x) (gdb) py-list 6 time.sleep(10) 7 8 9 def main(): 10 for x in range(10000): >11 do(x) 12 13 14 if __name__ == '__main__': 15 main() (gdb) py-print x local 'x' = 12 (gdb)
可以通过 py-down 回去:
(gdb) py-down #6 Frame 0xb74926e4, for file test.py, line 6, in do (x=12) time.sleep(10) (gdb) py-list 1 # -*- coding: utf-8 -*- 2 import time 3 4 5 def do(x): >6 time.sleep(10) 7 8 9 def main(): 10 for x in range(10000): 11 do(x) (gdb)
调试多线程程序¶
测试程序 test2.py:
# -*- coding: utf-8 -*-
from threading import Thread
import time
def do(x):
x = x * 3
time.sleep(x * 60)
def main():
threads = []
for x in range(1, 3):
t = Thread(target=do, args=(x,))
t.start()
for x in threads:
x.join()
if __name__ == '__main__':
main()
$ python test2.py & [2] 12281
查看所有线程¶
info threads
$ gdb python core.12281 (gdb) info threads Id Target Id Frame * 1 Thread 0xb74b9700 (LWP 11039) 0xb7711c31 in __kernel_vsyscall () 2 Thread 0xb73b8b40 (LWP 11040) 0xb7711c31 in __kernel_vsyscall () 3 Thread 0xb69ffb40 (LWP 11041) 0xb7711c31 in __kernel_vsyscall () (gdb)
可以看到这个程序当前有 3 个线程, 当前进入的是 1 号线程。
切换线程¶
thread ID
(gdb) thread 3
[Switching to thread 3 (Thread 0xb69ffb40 (LWP 11041))]
#0 0xb7711c31 in __kernel_vsyscall ()
(gdb) info threads
Id Target Id Frame
1 Thread 0xb74b9700 (LWP 11039) 0xb7711c31 in __kernel_vsyscall ()
2 Thread 0xb73b8b40 (LWP 11040) 0xb7711c31 in __kernel_vsyscall ()
* 3 Thread 0xb69ffb40 (LWP 11041) 0xb7711c31 in __kernel_vsyscall ()
(gdb)
现在切换到了 3 号线程。
可以通过前面所说的 py- 命令来查看当前线程的其他信息：
[Current thread is 1 (Thread 0xb74b9700 (LWP 11039))]
(gdb) py-list
335 waiter.acquire()
336 self.__waiters.append(waiter)
337 saved_state = self._release_save()
338 try: # restore state no matter what (e.g., KeyboardInterrupt)
339 if timeout is None:
>340 waiter.acquire()
341 if __debug__:
342 self._note("%s.wait(): got it", self)
343 else:
344 # Balancing act: We can't afford a pure busy loop, so we
345 # have to sleep; but if we sleep the whole timeout time,
(gdb) thread 2
[Switching to thread 2 (Thread 0xb73b8b40 (LWP 11040))]
#0 0xb7711c31 in __kernel_vsyscall ()
(gdb) py-list
3 import time
4
5
6 def do(x):
7 x = x * 3
>8 time.sleep(x * 60)
9
10
11 def main():
12 threads = []
13 for x in range(1, 3):
(gdb)
同时操作所有线程¶
thread apply all CMD 或 t a a CMD
(gdb) thread apply all py-list
Thread 3 (Thread 0xb69ffb40 (LWP 11041)):
3 import time
4
5
6 def do(x):
7 x = x * 3
>8 time.sleep(x * 60)
9
10
11 def main():
12 threads = []
13 for x in range(1, 3):
Thread 2 (Thread 0xb73b8b40 (LWP 11040)):
3 import time
4
5
6 def do(x):
7 x = x * 3
>8 time.sleep(x * 60)
9
10
11 def main():
12 threads = []
13 for x in range(1, 3):
---Type <return> to continue, or q <return> to quit---
Thread 1 (Thread 0xb74b9700 (LWP 11039)):
335 waiter.acquire()
336 self.__waiters.append(waiter)
337 saved_state = self._release_save()
338 try: # restore state no matter what (e.g., KeyboardInterrupt)
339 if timeout is None:
>340 waiter.acquire()
341 if __debug__:
342 self._note("%s.wait(): got it", self)
343 else:
344 # Balancing act: We can't afford a pure busy loop, so we
345 # have to sleep; but if we sleep the whole timeout time,
(gdb)
常用的 gdb python 相关的操作就是这些， 同时也不要忘记原来的 gdb 命令都是可以使用的哦。
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