使用 GDB 來為 C API 擴充功能和 CPython 內部偵錯
***********************************************

本文件解釋如何將 Python GDB 擴充功能 "python-gdb.py" 與 GDB 偵錯器一起
使用來為 CPython 擴充功能和 CPython 直譯器本身偵錯。

在為崩潰或死鎖等低階問題幀錯時，低階偵錯器（例如 GDB）對於診斷和修正問
題非常有用。預設情況下，GDB（或其任何前端）不支援特定於 CPython 直譯器
的高階資訊。

"python-gdb.py" 擴充功能將 CPython 直譯器資訊新增至 GDB。此擴充有助於
內省 (introspect) 目前執行的 Python 函式的堆疊。給定一個由 PyObject*
指標表示的 Python 物件，擴充功能會顯示該物件的型別和值。

正在開發 CPython 擴充功能或修補用 C 編寫之 CPython 部分的開發人員可以
使用本文件來學習如何將 "python-gdb.py" 擴充功能與 GDB 一起使用。

備註:

  本文件假設你熟悉 GDB 和 CPython C API 的基礎知識。它整合了 devguide
  和 Python wiki 的指引。


先決條件
========

你需要有：

* GDB 7 或更之後的版本。（對於早期版本的 GDB，請參閱 Python 3.11 或更
  早版本的原始程式碼中的 "Misc/gdbinit"。）

* 對 Python 和你在偵錯的任何擴充功能來說的與 GDB 相容的偵錯資訊。

* "python-gdb.py" 擴充。

該擴充功能是用 Python 建置的，但可能會單獨發布或根本不發布。以下我們將
一些常見系統的提示作為範例。請注意，即使說明與你的系統匹配，它們也可能
已過時。


使用從原始碼建置的 Python 進行設定
----------------------------------

當你從原始程式碼建立 CPython 時，偵錯資訊應該可用，並且建置應該將
"python-gdb.py" 檔案新增至儲存庫的根目錄中。

若要啟用支援，你必須將包含 "python-gdb.py" 的目錄新增至 GDB 的 "auto-
load-safe-path"。如果你還沒有這樣做，最新版本的 GDB 將列印警告，其中包
含有關如何執行此操作的說明。

備註:

  如果你沒有看到適合你的 GDB 版本的說明，請將其放入你的設定檔中（
  "~/.gdbinit" 或 "~/.config/gdb/gdbinit"）：

     add-auto-load-safe-path /path/to/cpython

  你也可以新增多個路徑，要以 ":" 分隔。


從 Linux 發行版設定 Python
--------------------------

大多數 Linux 系統在名為 "python-debuginfo"、"python-dbg" 或類似的套件
中提供系統 Python 的偵錯資訊。例如：

* Fedora：

        sudo dnf install gdb
        sudo dnf debuginfo-install python3

* Ubuntu：

        sudo apt install gdb python3-dbg

在最近的幾個 Linux 系統上，GDB 可以使用 *debuginfod* 自動下載偵錯符號
。但是這不會安裝 "python-gdb.py" 擴充功能；你通常需要另外安裝偵錯資訊
套件。


使用偵錯建置與使用開發模式
==========================

為了更輕鬆地進行偵錯，你可能需要：

* 使用 Python 的偵錯建置。（從原始碼建置時，請使用 "configure --with-
  pydebug"。在 Linux 發行版上，安裝並執行諸如 "python-debug" 或
  "python-dbg" 之類的套件（如果可用））。

* 使用 runtime 開發模式 ("-X dev")。

兩者都啟用額外的斷言 (assertion) 並停用一些最佳化。有時這會隱藏你試圖
想尋找的錯誤，但在大多數情況下，它們會使過程變得更容易。


使用 "python-gdb" 擴充功能
==========================

載入擴充功能後，它提供兩個主要功能：Python 值的漂亮列印器和附加命令。


漂亮列印器
----------

這是啟用此擴充功能時 GDB 回溯 (backtrace) 的樣子（有被截斷）：

   #0  0x000000000041a6b1 in PyObject_Malloc (nbytes=Cannot access memory at address 0x7fffff7fefe8
   ) at Objects/obmalloc.c:748
   #1  0x000000000041b7c0 in _PyObject_DebugMallocApi (id=111 'o', nbytes=24) at Objects/obmalloc.c:1445
   #2  0x000000000041b717 in _PyObject_DebugMalloc (nbytes=24) at Objects/obmalloc.c:1412
   #3  0x000000000044060a in _PyUnicode_New (length=11) at Objects/unicodeobject.c:346
   #4  0x00000000004466aa in PyUnicodeUCS2_DecodeUTF8Stateful (s=0x5c2b8d "__lltrace__", size=11, errors=0x0, consumed=
       0x0) at Objects/unicodeobject.c:2531
   #5  0x0000000000446647 in PyUnicodeUCS2_DecodeUTF8 (s=0x5c2b8d "__lltrace__", size=11, errors=0x0)
       at Objects/unicodeobject.c:2495
   #6  0x0000000000440d1b in PyUnicodeUCS2_FromStringAndSize (u=0x5c2b8d "__lltrace__", size=11)
       at Objects/unicodeobject.c:551
   #7  0x0000000000440d94 in PyUnicodeUCS2_FromString (u=0x5c2b8d "__lltrace__") at Objects/unicodeobject.c:569
   #8  0x0000000000584abd in PyDict_GetItemString (v=
       {'Yuck': <type at remote 0xad4730>, '__builtins__': <module at remote 0x7ffff7fd5ee8>, '__file__': 'Lib/test/crashers/nasty_eq_vs_dict.py', '__package__': None, 'y': <Yuck(i=0) at remote 0xaacd80>, 'dict': {0: 0, 1: 1, 2: 2, 3: 3}, '__name__': '__main__', 'z': <Yuck(i=0) at remote 0xaace60>, '__doc__': None}, key=
       0x5c2b8d "__lltrace__") at Objects/dictobject.c:2171

請注意 "PyDict_GetItemString" 的字典引數如何顯示為其 "repr()"，而不是
不透明的 "PyObject *" 指標。

該擴充功能透過為 "PyObject *" 型別的值提供自訂列印例程來運作。如果需要
存取物件較低階的詳細資訊，請將值轉換為適當型別的指標。例如：

   (gdb) p globals
   $1 = {'__builtins__': <module at remote 0x7ffff7fb1868>, '__name__':
   '__main__', 'ctypes': <module at remote 0x7ffff7f14360>, '__doc__': None,
   '__package__': None}

   (gdb) p *(PyDictObject*)globals
   $2 = {ob_refcnt = 3, ob_type = 0x3dbdf85820, ma_fill = 5, ma_used = 5,
   ma_mask = 7, ma_table = 0x63d0f8, ma_lookup = 0x3dbdc7ea70
   <lookdict_string>, ma_smalltable = {{me_hash = 7065186196740147912,
   me_key = '__builtins__', me_value = <module at remote 0x7ffff7fb1868>},
   {me_hash = -368181376027291943, me_key = '__name__',
   me_value ='__main__'}, {me_hash = 0, me_key = 0x0, me_value = 0x0},
   {me_hash = 0, me_key = 0x0, me_value = 0x0},
   {me_hash = -9177857982131165996, me_key = 'ctypes',
   me_value = <module at remote 0x7ffff7f14360>},
   {me_hash = -8518757509529533123, me_key = '__doc__', me_value = None},
   {me_hash = 0, me_key = 0x0, me_value = 0x0}, {
     me_hash = 6614918939584953775, me_key = '__package__', me_value = None}}}

請注意，漂亮列印器其實並不呼叫 "repr()"。對於基本型別，他們嘗試緊密匹
配其結果。

一個可能令人困惑的地方是，某些型別的自訂列印器看起來很像 GDB 標準類型
的內建列印器。例如，Python "int" (PyLongObject*) 的漂亮列印器給出的表
示法無法與常規機器層級整數之其一區分：

   (gdb) p some_machine_integer
   $3 = 42

   (gdb) p some_python_integer
   $4 = 42

可以透過轉換 (cast) 為 PyLongObject* 來揭示內部結構：

   (gdb) p *(PyLongObject*)some_python_integer
   $5 = {ob_base = {ob_base = {ob_refcnt = 8, ob_type = 0x3dad39f5e0}, ob_size = 1},
   ob_digit = {42}}

使用 "str" 型別時也可能會出現類似的困惑，其中的輸出看起來很像對於
"char *" 的 gdb 內建列印器 ：

   (gdb) p ptr_to_python_str
   $6 = '__builtins__'

"str" 實例的漂亮列印器預設使用單引號（Python 的 "repr" 對於字串也是如
此），而 "char *" 值的標準列印器使用雙引號並包含十六進位位址：

   (gdb) p ptr_to_char_star
   $7 = 0x6d72c0 "hello world"

同樣，可以透過轉換為 PyUnicodeObject* 來揭示實作細節：

   (gdb) p *(PyUnicodeObject*)$6
   $8 = {ob_base = {ob_refcnt = 33, ob_type = 0x3dad3a95a0}, length = 12,
   str = 0x7ffff2128500, hash = 7065186196740147912, state = 1, defenc = 0x0}


"py-list"
---------

   該擴充功能新增了一個 "py-list" 命令，該命令列出了所選執行緒中目前
   frame 的 Python 原始程式碼（如果有）。目前的列會標有 ">"：

      (gdb) py-list
       901        if options.profile:
       902            options.profile = False
       903            profile_me()
       904            return
       905
      >906        u = UI()
       907        if not u.quit:
       908            try:
       909                gtk.main()
       910            except KeyboardInterrupt:
       911                # properly quit on a keyboard interrupt...

   使用 "py-list START" 列出 Python 原始碼中不同的列號，使用 "py-list
   START,END" 列出 Python 原始碼中特定範圍的列。


"py-up" 和 "py-down"
--------------------

   "py-up" 和 "py-down" 命令類似於 GDB 的常規 "up" 和 "down" 命令，但
   嘗試在 CPython frame 層級移動，而不是 C frame。

   GDB 並不總是能夠讀取相關的 frame 資訊，這取決於編譯 CPython 的最佳
   化等級。在內部，這些指令會尋找正在執行預設 frame 計算 (evaluation)
   函式（即 CPython 中迴圈的核心位元組碼直譯器）的 C frame，並尋找相關
   "PyFrameObject *" 的值。

   它們在執行緒內發出（於 C 層級的）frame 編號。

   例如：

      (gdb) py-up
      #37 Frame 0x9420b04, for file /usr/lib/python2.6/site-packages/
      gnome_sudoku/main.py, line 906, in start_game ()
          u = UI()
      (gdb) py-up
      #40 Frame 0x948e82c, for file /usr/lib/python2.6/site-packages/
      gnome_sudoku/gnome_sudoku.py, line 22, in start_game(main=<module at remote 0xb771b7f4>)
          main.start_game()
      (gdb) py-up
      Unable to find an older python frame

   所以現在我們處於 Python 堆疊的頂端。

   frame 編號與 GDB 標準 "backtrace" 指令顯示的 frame 編號相對應。此指
   令會跳過不執行 Python 程式碼的 C frame。

   回到下面：

      (gdb) py-down
      #37 Frame 0x9420b04, for file /usr/lib/python2.6/site-packages/gnome_sudoku/main.py, line 906, in start_game ()
          u = UI()
      (gdb) py-down
      #34 (unable to read python frame information)
      (gdb) py-down
      #23 (unable to read python frame information)
      (gdb) py-down
      #19 (unable to read python frame information)
      (gdb) py-down
      #14 Frame 0x99262ac, for file /usr/lib/python2.6/site-packages/gnome_sudoku/game_selector.py, line 201, in run_swallowed_dialog (self=<NewOrSavedGameSelector(new_game_model=<gtk.ListStore at remote 0x98fab44>, puzzle=None, saved_games=[{'gsd.auto_fills': 0, 'tracking': {}, 'trackers': {}, 'notes': [], 'saved_at': 1270084485, 'game': '7 8 0 0 0 0 0 5 6 0 0 9 0 8 0 1 0 0 0 4 6 0 0 0 0 7 0 6 5 0 0 0 4 7 9 2 0 0 0 9 0 1 0 0 0 3 9 7 6 0 0 0 1 8 0 6 0 0 0 0 2 8 0 0 0 5 0 4 0 6 0 0 2 1 0 0 0 0 0 4 5\n7 8 0 0 0 0 0 5 6 0 0 9 0 8 0 1 0 0 0 4 6 0 0 0 0 7 0 6 5 1 8 3 4 7 9 2 0 0 0 9 0 1 0 0 0 3 9 7 6 0 0 0 1 8 0 6 0 0 0 0 2 8 0 0 0 5 0 4 0 6 0 0 2 1 0 0 0 0 0 4 5', 'gsd.impossible_hints': 0, 'timer.__absolute_start_time__': <float at remote 0x984b474>, 'gsd.hints': 0, 'timer.active_time': <float at remote 0x984b494>, 'timer.total_time': <float at remote 0x984b464>}], dialog=<gtk.Dialog at remote 0x98faaa4>, saved_game_model=<gtk.ListStore at remote 0x98fad24>, sudoku_maker=<SudokuMaker(terminated=False, played=[], batch_siz...(truncated)
                  swallower.run_dialog(self.dialog)
      (gdb) py-down
      #11 Frame 0x9aead74, for file /usr/lib/python2.6/site-packages/gnome_sudoku/dialog_swallower.py, line 48, in run_dialog (self=<SwappableArea(running=<gtk.Dialog at remote 0x98faaa4>, main_page=0) at remote 0x98fa6e4>, d=<gtk.Dialog at remote 0x98faaa4>)
                  gtk.main()
      (gdb) py-down
      #8 (unable to read python frame information)
      (gdb) py-down
      Unable to find a newer python frame

   我們現在處於 Python 堆疊的底部。

   請注意，在 Python 3.12 及更高版本中，同一個 C 堆疊 frame 可用於多個
   Python 堆疊 frame。這意味著 "py-up" 和 "py-down" 可以一次移動多個
   Python frame。例如：

      (gdb) py-up
      #6 Frame 0x7ffff7fb62b0, for file /tmp/rec.py, line 5, in recursive_function (n=0)
         time.sleep(5)
      #6 Frame 0x7ffff7fb6240, for file /tmp/rec.py, line 7, in recursive_function (n=1)
         recursive_function(n-1)
      #6 Frame 0x7ffff7fb61d0, for file /tmp/rec.py, line 7, in recursive_function (n=2)
         recursive_function(n-1)
      #6 Frame 0x7ffff7fb6160, for file /tmp/rec.py, line 7, in recursive_function (n=3)
         recursive_function(n-1)
      #6 Frame 0x7ffff7fb60f0, for file /tmp/rec.py, line 7, in recursive_function (n=4)
         recursive_function(n-1)
      #6 Frame 0x7ffff7fb6080, for file /tmp/rec.py, line 7, in recursive_function (n=5)
         recursive_function(n-1)
      #6 Frame 0x7ffff7fb6020, for file /tmp/rec.py, line 9, in <module> ()
         recursive_function(5)
      (gdb) py-up
      Unable to find an older python frame


"py-bt"
-------

   "py-bt" 指令嘗試顯示目前執行緒的 Python 層級回溯。

   例如：

      (gdb) py-bt
      #8 (unable to read python frame information)
      #11 Frame 0x9aead74, for file /usr/lib/python2.6/site-packages/gnome_sudoku/dialog_swallower.py, line 48, in run_dialog (self=<SwappableArea(running=<gtk.Dialog at remote 0x98faaa4>, main_page=0) at remote 0x98fa6e4>, d=<gtk.Dialog at remote 0x98faaa4>)
                  gtk.main()
      #14 Frame 0x99262ac, for file /usr/lib/python2.6/site-packages/gnome_sudoku/game_selector.py, line 201, in run_swallowed_dialog (self=<NewOrSavedGameSelector(new_game_model=<gtk.ListStore at remote 0x98fab44>, puzzle=None, saved_games=[{'gsd.auto_fills': 0, 'tracking': {}, 'trackers': {}, 'notes': [], 'saved_at': 1270084485, 'game': '7 8 0 0 0 0 0 5 6 0 0 9 0 8 0 1 0 0 0 4 6 0 0 0 0 7 0 6 5 0 0 0 4 7 9 2 0 0 0 9 0 1 0 0 0 3 9 7 6 0 0 0 1 8 0 6 0 0 0 0 2 8 0 0 0 5 0 4 0 6 0 0 2 1 0 0 0 0 0 4 5\n7 8 0 0 0 0 0 5 6 0 0 9 0 8 0 1 0 0 0 4 6 0 0 0 0 7 0 6 5 1 8 3 4 7 9 2 0 0 0 9 0 1 0 0 0 3 9 7 6 0 0 0 1 8 0 6 0 0 0 0 2 8 0 0 0 5 0 4 0 6 0 0 2 1 0 0 0 0 0 4 5', 'gsd.impossible_hints': 0, 'timer.__absolute_start_time__': <float at remote 0x984b474>, 'gsd.hints': 0, 'timer.active_time': <float at remote 0x984b494>, 'timer.total_time': <float at remote 0x984b464>}], dialog=<gtk.Dialog at remote 0x98faaa4>, saved_game_model=<gtk.ListStore at remote 0x98fad24>, sudoku_maker=<SudokuMaker(terminated=False, played=[], batch_siz...(truncated)
                  swallower.run_dialog(self.dialog)
      #19 (unable to read python frame information)
      #23 (unable to read python frame information)
      #34 (unable to read python frame information)
      #37 Frame 0x9420b04, for file /usr/lib/python2.6/site-packages/gnome_sudoku/main.py, line 906, in start_game ()
          u = UI()
      #40 Frame 0x948e82c, for file /usr/lib/python2.6/site-packages/gnome_sudoku/gnome_sudoku.py, line 22, in start_game (main=<module at remote 0xb771b7f4>)
          main.start_game()

   The frame numbers correspond to those displayed by GDB's standard
   "backtrace" command.


"py-print"
----------

   "py-print" 命令查找 Python 名稱並嘗試列印它。它在目前執行緒中尋找局
   部變數，然後是全域變數，最後是內建變數：

      (gdb) py-print self
      local 'self' = <SwappableArea(running=<gtk.Dialog at remote 0x98faaa4>,
      main_page=0) at remote 0x98fa6e4>
      (gdb) py-print __name__
      global '__name__' = 'gnome_sudoku.dialog_swallower'
      (gdb) py-print len
      builtin 'len' = <built-in function len>
      (gdb) py-print scarlet_pimpernel
      'scarlet_pimpernel' not found

   如果目前 C frame 對應多個 Python frame，則 "py-print" 僅考慮第一個
   。


"py-locals"
-----------

   "py-locals" 命令尋找所選執行緒中目前 Python frame 內的所有 Python
   局部變數，並列印它們的表示：

      (gdb) py-locals
      self = <SwappableArea(running=<gtk.Dialog at remote 0x98faaa4>,
      main_page=0) at remote 0x98fa6e4>
      d = <gtk.Dialog at remote 0x98faaa4>

   如果目前 C frame 對應於多個 Python frame，則會顯示所有這些 frame 的
   局部變數：

      (gdb) py-locals
      Locals for recursive_function
      n = 0
      Locals for recursive_function
      n = 1
      Locals for recursive_function
      n = 2
      Locals for recursive_function
      n = 3
      Locals for recursive_function
      n = 4
      Locals for recursive_function
      n = 5
      Locals for <module>


與 GDB 指令一起使用
===================

擴充命令補充了 GDB 的內建命令。例如，你可以將 "py-bt" 顯示的 frame 編
號與 "frame" 命令一同使用來跳到所選執行緒中的特定 frame，如下所示：

   (gdb) py-bt
   (output snipped)
   #68 Frame 0xaa4560, for file Lib/test/regrtest.py, line 1548, in <module> ()
           main()
   (gdb) frame 68
   #68 0x00000000004cd1e6 in PyEval_EvalFrameEx (f=Frame 0xaa4560, for file Lib/test/regrtest.py, line 1548, in <module> (), throwflag=0) at Python/ceval.c:2665
   2665                            x = call_function(&sp, oparg);
   (gdb) py-list
   1543        # 在暫時改變 CWD 到一個臨時且可寫入的目錄的
   1544        # 情境管理器中運行測試。
   1545        # 如果無法建立或更改 CWD，則使用原始的 CWD。
   1546        # 原始 CWD 可從 test_support.SAVEDCWD 獲得。
   1547        with test_support.temp_cwd(TESTCWD, quiet=True):
   >1548            main()

"info threads" 命令將為你提供行程內的執行緒串列，你可以使用 "thread"
命令選擇不同的執行緒：

   (gdb) info threads
     105 Thread 0x7fffefa18710 (LWP 10260)  sem_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/sem_wait.S:86
     104 Thread 0x7fffdf5fe710 (LWP 10259)  sem_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/sem_wait.S:86
   * 1 Thread 0x7ffff7fe2700 (LWP 10145)  0x00000038e46d73e3 in select () at ../sysdeps/unix/syscall-template.S:82

你可以使用 "thread apply all COMMAND"（或簡短地用 "t a a COMMAND"）在
所有執行緒上執行命令。使用 "py-bt" 你可以看到每個執行緒在 Python 層級
正在做什麼：

   (gdb) t a a py-bt

   Thread 105 (Thread 0x7fffefa18710 (LWP 10260)):
   #5 Frame 0x7fffd00019d0, for file /home/david/coding/python-svn/Lib/threading.py, line 155, in _acquire_restore (self=<_RLock(_Verbose__verbose=False, _RLock__owner=140737354016512, _RLock__block=<thread.lock at remote 0x858770>, _RLock__count=1) at remote 0xd7ff40>, count_owner=(1, 140737213728528), count=1, owner=140737213728528)
           self.__block.acquire()
   #8 Frame 0x7fffac001640, for file /home/david/coding/python-svn/Lib/threading.py, line 269, in wait (self=<_Condition(_Condition__lock=<_RLock(_Verbose__verbose=False, _RLock__owner=140737354016512, _RLock__block=<thread.lock at remote 0x858770>, _RLock__count=1) at remote 0xd7ff40>, acquire=<instancemethod at remote 0xd80260>, _is_owned=<instancemethod at remote 0xd80160>, _release_save=<instancemethod at remote 0xd803e0>, release=<instancemethod at remote 0xd802e0>, _acquire_restore=<instancemethod at remote 0xd7ee60>, _Verbose__verbose=False, _Condition__waiters=[]) at remote 0xd7fd10>, timeout=None, waiter=<thread.lock at remote 0x858a90>, saved_state=(1, 140737213728528))
               self._acquire_restore(saved_state)
   #12 Frame 0x7fffb8001a10, for file /home/david/coding/python-svn/Lib/test/lock_tests.py, line 348, in f ()
               cond.wait()
   #16 Frame 0x7fffb8001c40, for file /home/david/coding/python-svn/Lib/test/lock_tests.py, line 37, in task (tid=140737213728528)
                   f()

   Thread 104 (Thread 0x7fffdf5fe710 (LWP 10259)):
   #5 Frame 0x7fffe4001580, for file /home/david/coding/python-svn/Lib/threading.py, line 155, in _acquire_restore (self=<_RLock(_Verbose__verbose=False, _RLock__owner=140737354016512, _RLock__block=<thread.lock at remote 0x858770>, _RLock__count=1) at remote 0xd7ff40>, count_owner=(1, 140736940992272), count=1, owner=140736940992272)
           self.__block.acquire()
   #8 Frame 0x7fffc8002090, for file /home/david/coding/python-svn/Lib/threading.py, line 269, in wait (self=<_Condition(_Condition__lock=<_RLock(_Verbose__verbose=False, _RLock__owner=140737354016512, _RLock__block=<thread.lock at remote 0x858770>, _RLock__count=1) at remote 0xd7ff40>, acquire=<instancemethod at remote 0xd80260>, _is_owned=<instancemethod at remote 0xd80160>, _release_save=<instancemethod at remote 0xd803e0>, release=<instancemethod at remote 0xd802e0>, _acquire_restore=<instancemethod at remote 0xd7ee60>, _Verbose__verbose=False, _Condition__waiters=[]) at remote 0xd7fd10>, timeout=None, waiter=<thread.lock at remote 0x858860>, saved_state=(1, 140736940992272))
               self._acquire_restore(saved_state)
   #12 Frame 0x7fffac001c90, for file /home/david/coding/python-svn/Lib/test/lock_tests.py, line 348, in f ()
               cond.wait()
   #16 Frame 0x7fffac0011c0, for file /home/david/coding/python-svn/Lib/test/lock_tests.py, line 37, in task (tid=140736940992272)
                   f()

   Thread 1 (Thread 0x7ffff7fe2700 (LWP 10145)):
   #5 Frame 0xcb5380, for file /home/david/coding/python-svn/Lib/test/lock_tests.py, line 16, in _wait ()
       time.sleep(0.01)
   #8 Frame 0x7fffd00024a0, for file /home/david/coding/python-svn/Lib/test/lock_tests.py, line 378, in _check_notify (self=<ConditionTests(_testMethodName='test_notify', _resultForDoCleanups=<TestResult(_original_stdout=<cStringIO.StringO at remote 0xc191e0>, skipped=[], _mirrorOutput=False, testsRun=39, buffer=False, _original_stderr=<file at remote 0x7ffff7fc6340>, _stdout_buffer=<cStringIO.StringO at remote 0xc9c7f8>, _stderr_buffer=<cStringIO.StringO at remote 0xc9c790>, _moduleSetUpFailed=False, expectedFailures=[], errors=[], _previousTestClass=<type at remote 0x928310>, unexpectedSuccesses=[], failures=[], shouldStop=False, failfast=False) at remote 0xc185a0>, _threads=(0,), _cleanups=[], _type_equality_funcs={<type at remote 0x7eba00>: <instancemethod at remote 0xd750e0>, <type at remote 0x7e7820>: <instancemethod at remote 0xd75160>, <type at remote 0x7e30e0>: <instancemethod at remote 0xd75060>, <type at remote 0x7e7d20>: <instancemethod at remote 0xd751e0>, <type at remote 0x7f19e0...(truncated)
           _wait()
