Bugs item #1165761, was opened at 2005-03-18 05:18
Message generated for change (Comment added) made by mwh
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Category: Threads
Group: Python 2.4
Status: Open
Resolution: None
Priority: 5
Submitted By: Jeff Stearns (jeffstearns)
Assigned to: Nobody/Anonymous (nobody)
Summary: KeyboardInterrupt causes segmentation fault with threads
Initial Comment:
The attached sample program crashes Python 2.4.1c1 with a
segmentation fault if it is interupted.
I wrote a simple program which simulates multiple HTTP clients.
The program is mult-threaded.
It runs on Debian with a 2.6 kernel.
If the program is interrupted (via ^C), Python 2.4.1c1 takes a
segmentation fault.
Investigation with gdb shows that the error occurs within
PyEval_EvalFrame at line 1661 below.
It's executing an END_FINALLY bytecode.
The offending statement is
v = POP();
The value of v is 0.
This is then passed to PyInt_Check(), which attempts to dereference
a NULL pointer.
1659 case END_FINALLY:
1660 v = POP();
1661 if (PyInt_Check(v)) {
1662 why = (enum why_code)
PyInt_AS_LONG(v);
1663 assert(why != WHY_YIELD);
1664 if (why == WHY_RETURN ||
1665 why == WHY_CONTINUE)
1666 retval = POP();
1667 }
#0 PyEval_EvalFrame (f=0x821cd04) at Python/ceval.c:1661
#1 0x080ae6bd in fast_function (func=0x4030df8d,
pp_stack=0xbfffe85c, n=1, na=1076944740, nk=1079484852) at
Python/ceval.c:3629
#2 0x080ae254 in call_function (pp_stack=0xbfffe85c,
oparg=1076944740) at Python/ceval.c:3568
#3 0x080ac7a6 in PyEval_EvalFrame (f=0x8227d04) at Python/
ceval.c:2163
#4 0x080ad21e in PyEval_EvalCodeEx (co=0x4037e660,
globals=0x4030df64, locals=0x4030df8d, args=0x40295c78,
argcount=1, kws=0x0, kwcount=0, defs=0x0, defcount=0,
closure=0x0)
at Python/ceval.c:2730
#5 0x08105647 in function_call (func=0x4038a304,
arg=0x40295c6c, kw=0x0) at Objects/funcobject.c:548
#6 0x0805c409 in PyObject_Call (func=0x8148088,
arg=0x4030df64, kw=0x4030df64) at Objects/abstract.c:1751
#7 0x08062e38 in instancemethod_call (func=0x4038a304,
arg=0x40295c6c, kw=0x4030df64) at Objects/classobject.c:2431
#8 0x0805c409 in PyObject_Call (func=0x8148088,
arg=0x4030df64, kw=0x4030df64) at Objects/abstract.c:1751
#9 0x080ae0e7 in PyEval_CallObjectWithKeywords
(func=0x4030df64, arg=0x4028702c, kw=0x405785a4) at Python/
ceval.c:3419
#10 0x0809101c in slot_tp_del (self=0x4057a1b4) at Objects/
typeobject.c:4818
#11 0x08086f93 in subtype_dealloc (self=0x4057a1b4) at Objects/
typeobject.c:669
#12 0x08062a4c in instancemethod_dealloc (im=0x4057857c) at
Objects/classobject.c:2225
#13 0x080790a4 in dict_dealloc (mp=0x4056aacc) at Objects/
dictobject.c:734
#14 0x0805e544 in instance_dealloc (inst=0x40569dcc) at Objects/
classobject.c:687
#15 0x081042cb in frame_dealloc (f=0x8218f14) at Objects/
frameobject.c:418
#16 0x080dc1e9 in PyThreadState_Clear (tstate=0x81f9820) at
Python/pystate.c:217
#17 0x080dbdf8 in PyInterpreterState_Clear (interp=0x8148048) at
Python/pystate.c:93
#18 0x080dcef2 in Py_Finalize () at Python/pythonrun.c:408
#19 0x08055391 in Py_Main (argc=1, argv=0xbfffee14) at Modules/
main.c:504
#20 0x08054eeb in main (argc=1076944740, argv=0x4030df64) at
Modules/python.c:23
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>Comment By: Michael Hudson (mwh)
Date: 2005-03-18 15:30
Message:
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Chop chop chop. Attached seems fairly minimal. It's
something to do with exception handling in __del__ methods
that are called during interpreter tear down.
----------------------------------------------------------------------
Comment By: Michael Hudson (mwh)
Date: 2005-03-18 14:53
Message:
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Duh, most of that was in the original report :)
----------------------------------------------------------------------
Comment By: Michael Hudson (mwh)
Date: 2005-03-18 14:52
Message:
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And on linux too.
Gdb poking finds that the crash is in
socket._fileobject.close which is being called from
socket._fileobject.__del__ which is being called from ...
PyThreadState_Clear, PyInterpreterState_Clear, Py_Finalize.
So I still think it's some kind of tear-down horror. Hmm.
----------------------------------------------------------------------
Comment By: Jarek Zgoda (zgoda)
Date: 2005-03-18 14:15
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2.4 crashes also on Windows.
----------------------------------------------------------------------
Comment By: Michael Hudson (mwh)
Date: 2005-03-18 09:56
Message:
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Oh, and I should say, I'm on OS X.
----------------------------------------------------------------------
Comment By: Michael Hudson (mwh)
Date: 2005-03-18 09:53
Message:
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Does this always dump core for you? When I ^C CVS HEAD running this
a variety of nasty things happen, including one core dump and one "Fatal
Python error: PyImport_GetModuleDict: no module dictionary!", but more
often it's something like:
cccc^CTraceback (most recent call last):
File "/Users/mwh/Desktop/thread_crash.py", line 67, in ?
main(sys.argv)
File "/Users/mwh/Desktop/thread_crash.py", line 64, in main
run (20)
File "/Users/mwh/Desktop/thread_crash.py", line 56, in run
thread.start ()
File "/Users/mwh/Source/python/dist/src/Lib/threading.py", line 418, in
start
_sleep(0.000001) # 1 usec, to let the thread run (Solaris hack)
KeyboardInterrupt
Exception in thread Thread-4 (most likely raised during interpreter
shutdown):
Traceback (most recent call last):
File "/Users/mwh/Source/python/dist/src/Lib/threading.py", line 442, in
__bootstrap
File "/Users/mwh/Source/python/dist/src/Lib/threading.py", line 422, in
run
File "/Users/mwh/Desktop/thread_crash.py", line 23, in run
File "/Users/mwh/Desktop/thread_crash.py", line 33, in runOnce
File "/Users/mwh/Source/python/dist/src/Lib/urllib2.py", line 129, in
urlopen
File "/Users/mwh/Source/python/dist/src/Lib/urllib2.py", line 439, in
build_opener
File "/Users/mwh/Source/python/dist/src/Lib/urllib2.py", line 291, in
add_handler
<class 'exceptions.TypeError'>: 'NoneType' object is not callable
Unhandled exception in thread started by
Error in sys.excepthook:
Original exception was:
Exception in thread Thread-2 (most likely raised during interpreter
shutdown):
Traceback (most recent call last):
File "/Users/mwh/Source/python/dist/src/Lib/threading.py", line 442, in
__bootstrap
File "/Users/mwh/Source/python/dist/src/Lib/threading.py", line 422, in
run
File "/Users/mwh/Desktop/thread_crash.py", line 23, in run
File "/Users/mwh/Desktop/thread_crash.py", line 33, in runOnce
File "/Users/mwh/Source/python/dist/src/Lib/urllib2.py", line 129, in
urlopen
File "/Users/mwh/Source/python/dist/src/Lib/urllib2.py", line 439, in
build_opener
File "/Users/mwh/Source/python/dist/src/Lib/urllib2.py", line 291, in
add_handler
<class 'exceptions.TypeError'>: 'NoneType' object is not callable
Unhandled exception in thread started by
Error in sys.excepthook:
Original exception was:
with the last bit repeated a few times.
At a guess, it's some kind of interpreter tear-down horror.
Python 2.3 seems to behave much more sensibly.
----------------------------------------------------------------------
Comment By: Michael Hudson (mwh)
Date: 2005-03-18 09:00
Message:
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Can you try 2.3? There were some changes in the area for 2.4.
I'll try to poke at it too.
----------------------------------------------------------------------
Comment By: Jeff Stearns (jeffstearns)
Date: 2005-03-18 06:44
Message:
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The bug also exists when Python is compiled with --with-pydebug:
% ./python2.4 -c 'import clientLoadSimulator; clientLoadSimulator.run(20)'
cccccccccccccCc.cCcCccCcc.CCC..CCC......C...........C.C..Traceback (most
recent call last):
File "<string>", line 1, in ?
File "clientLoadSimulator.py", line 67, in run
thread.join (1.0)
File "/usr/local/lib/python2.4/threading.py", line 550, in join
self.__block.wait(delay)
File "/usr/local/lib/python2.4/threading.py", line 222, in wait
_sleep(delay)
KeyboardInterrupt
[29492 refs]
Segmentation fault (core dumped)
----------------------------------------------------------------------
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