gdb 调试python 进程，包括core dump 调试

设置core dump 文件生成目录
https://blog.csdn.net/chengde6896383/article/details/83345684

使用 gdb 调试运行中的 Python 进程
https://mozillazg.com/2017/07/debug-running-python-process-with-gdb.html

步骤一：开启core dump文件生成

ulimit -c unlimited

步骤二：设置core dump文件位置

vi /etc/sysctl.conf

修改（添加）如下两个变量

kernel.core_pattern =/var/core/core_%e_%p

kernel.core_uses_pid= 0

这里是改为生成目录在/var/core/，%e代表程序名称，%p是进程ID

如果想直接生成在可执行文件相同目录，前面不要加任何目录，直接

kernel.core_pattern =core_%e_%p

步骤三：让修改生效

sysctl -p/etc/sysctl.conf

测试环境¶
准备工作¶
生成 core file¶
可用的 python 相关的命令¶
当前执行位置的源码¶
当前位置的调用栈¶
查看变量的值¶
查看上层调用方的信息¶
调试多线程程序¶
- 查看所有线程¶
- 切换线程¶
- 同时操作所有线程¶
参考资料¶

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 timedef 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-list1    # -*- coding: utf-8 -*-2    import time345    def do(x):>6        time.sleep(10)789    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 dotime.sleep(10)File "test.py", line 11, in maindo(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-list1    # -*- coding: utf-8 -*-2    import time345    def do(x):>6        time.sleep(10)789    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-list6        time.sleep(10)789    def main():10        for x in range(10000):>11            do(x)121314    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-list1    # -*- coding: utf-8 -*-2    import time345    def do(x):>6        time.sleep(10)789    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 timedef do(x):x = x * 3time.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 threadsId   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 threadsId   Target Id         Frame1    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-list335            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 we345                    # 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-list3    import time456    def do(x):7        x = x * 3>8        time.sleep(x * 60)91011    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-listThread 3 (Thread 0xb69ffb40 (LWP 11041)):3    import time456    def do(x):7        x = x * 3>8        time.sleep(x * 60)91011    def main():12        threads = []13        for x in range(1, 3):Thread 2 (Thread 0xb73b8b40 (LWP 11040)):3    import time456    def do(x):7        x = x * 3>8        time.sleep(x * 60)91011    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 we345                    # 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。