gdb로python 디버깅

개시하다

언제 쓸 수 있을까요?

개발 환경

설정

# debuginfo-install python

# debuginfo-install python3 libgcc

사용법

$ gdb python <PID>

(gdb) source /usr/lib/debug/usr/lib64/libpython2.7.so.1.0.debug-gdb.py

(gdb) source /usr/lib/debug/usr/lib64/libpython3.6dm.so.1.0-3.6.8-18.el7.x86_64.debug-gdb.py

데모

import threading
import time

class MultiThreadDeadLock(object):
    '''
    MultiThreadDeadLock
    デッドロックを意図的におこすテスト用の実装
    '''

    def __init__(self):
        '''
        constructor
        '''
        self._counter = 0
        self.main()

    def increment(self, lock):
        '''
        カウンタをインクリメントします。
        :param lock: (object) threading.Lock()で取得した排他用オブジェクト
        :return: None
        '''
        while True:
            time.sleep(0.1) # スレッド間の割り込み用に少し待たせる
            lock.acquire()
            self._counter += 1
            lock.release()

    def print_counter(self, lock):
        '''
        現在のカウンタを表示します。
        デッドロックを再現するため3より大きい場合に意図的にロックを解放せずにExceptionをraiseします。
        :param lock: (object) threading.Lock()で取得した排他用オブジェクト
        :return: None
        '''
        while True:
            time.sleep(0.1) # スレッド間の割り込み用に少し待たせる
            lock.acquire()
            print("counter = {}".format(self._counter))
            if self._counter > 3:
                # 意図的にExceptionをraiseして、デッドロックさせる。
                # 実際には、予期しないところでExceptionがraiseされることだろう...
                raise RuntimeError()
            lock.release()

    def main(self):
        '''
        メイン処理
        :return: None
        '''
        lock = threading.Lock()

        inc_thread = threading.Thread(target=self.increment, args=(lock,))
        print_thread = threading.Thread(target=self.print_counter, args=(lock,))
        inc_thread.start()
        print_thread.start()
        inc_thread.join()
        print_thread.join()

if __name__ == '__main__':
    MultiThreadDeadLock()

$ gdb python3 7066
GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-115.el7
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-redhat-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /usr/bin/python3.6...Reading symbols from /usr/lib/debug/usr/bin/python3.6.debug...done.
done.
(中略)
done.
Loaded symbols for /lib64/libgcc_s.so.1
0x00007f5a083e8afb in futex_abstimed_wait (cancel=true, private=<optimized out>, 
    abstime=0x0, expected=0, futex=0x7f59fc000c10)
    at ../nptl/sysdeps/unix/sysv/linux/sem_waitcommon.c:43
43	      err = lll_futex_wait (futex, expected, private);
(gdb) source /usr/lib/debug/usr/lib64/libpython3.6dm.so.1.0-3.6.8-18.el7.x86_64.debug-gdb.py
(gdb) py-bt
Traceback (most recent call first):
  <built-in method acquire of _thread.lock object at remote 0x7f5a011328c8>
  File "/usr/lib64/python3.6/threading.py", line 1072, in _wait_for_tstate_lock
    elif lock.acquire(block, timeout):
  File "/usr/lib64/python3.6/threading.py", line 1056, in join
    self._wait_for_tstate_lock()
  File "pythondebuggdb.py", line 68, in main
    inc_thread.join()
  File "pythondebuggdb.py", line 26, in __init__
    self.main()
  File "pythondebuggdb.py", line 72, in <module>
    MultiThreadDeadLock()

(gdb) info threads
  Id   Target Id         Frame 
  2    Thread 0x7f5a01094700 (LWP 7067) "python3" 0x00007f5a083e8afb in futex_abstimed_wait (cancel=true, private=<optimized out>, abstime=0x0, expected=0, futex=0x2471020)
    at ../nptl/sysdeps/unix/sysv/linux/sem_waitcommon.c:43
* 1    Thread 0x7f5a08d20740 (LWP 7066) "python3" 0x00007f5a083e8afb in futex_abstimed_wait (cancel=true, private=<optimized out>, abstime=0x0, expected=0, futex=0x7f59fc000c10)
    at ../nptl/sysdeps/unix/sysv/linux/sem_waitcommon.c:43
(gdb) thread 2
[Switching to thread 2 (Thread 0x7f5a01094700 (LWP 7067))]
#0  0x00007f5a083e8afb in futex_abstimed_wait (cancel=true, private=<optimized out>, 
    abstime=0x0, expected=0, futex=0x2471020)
    at ../nptl/sysdeps/unix/sysv/linux/sem_waitcommon.c:43
43	      err = lll_futex_wait (futex, expected, private);

참고 문헌