New submission from STINNER Victor <[EMAIL PROTECTED]>:
BufferedWriter from Lib/io.py is thread-safe, but... the Python
instruction "with self._write_lock:" could be interrupted when the
lock is already acquired. Especially, _lsprof.Profiler() uses ceval
hook and is called when the lock is acquired. But if the profiler (or
any other module using the hook) re-use the stream (stdout or stderr),
we get a deadlock!?
Well, this problem is really not critical since only developers
profilers (really?).
Solution: use C implementation of Lib/io.py (from Python 2.6) to avoid
ceval hook?
Example with py3k trunk:
>>> import _lsprof
>>> prof=_lsprof.Profiler(42)
>>> prof.enable()
# _lsprof calls 42()
# -> 42 is not callable
# -> call PyErr_WriteUnraisable(<42 is not callable>)
# -> deadlock
Traceback example:
#6 0x080ecb30 in PyThread_acquire_lock (lock=0x820f550, waitflag=1)
at Python/thread_pthread.h:352
(...)
#8 0x08162521 in PyCFunction_Call (func=0x83abfbc, arg=0xb7dc6034,
kw=0x0) at Objects/methodobject.c:81
#9 0x080b3659 in call_function (pp_stack=0xbfbf9474, oparg=0) at
Python/ceval.c:3403
#10 0x080ae7a6 in PyEval_EvalFrameEx (f=0x83b9f94, throwflag=0) at
Python/ceval.c:2205
#11 0x080b3aae in fast_function (func=0x83a25b4, pp_stack=0xbfbf9724,
n=2, na=2, nk=0) at Python/ceval.c:3491
#12 0x080b37ef in call_function (pp_stack=0xbfbf9724, oparg=1) at
Python/ceval.c:3424
#13 0x080ae7a6 in PyEval_EvalFrameEx (f=0x83b981c, throwflag=0) at
Python/ceval.c:2205
#14 0x080b1aee in PyEval_EvalCodeEx (co=0x838a328, globals=0x8330534,
locals=0x0, args=0x8373da0, argcount=2, kws=0x0, kwcount=0, defs=0x0,
defcount=0, kwdefs=0x0, closure=0x0) at Python/ceval.c:2840
#15 0x0814ab2e in function_call (func=0x83a3b8c, arg=0x8373d8c,
kw=0x0) at Objects/funcobject.c:628
#16 0x08118d19 in PyObject_Call (func=0x83a3b8c, arg=0x8373d8c,
kw=0x0) at Objects/abstract.c:2181
#17 0x08132eb0 in method_call (func=0x83a3b8c, arg=0x8373d8c, kw=0x0)
at Objects/classobject.c:323
#18 0x08118d19 in PyObject_Call (func=0x83037dc, arg=0x83141f4,
kw=0x0) at Objects/abstract.c:2181
#19 0x080b2ed8 in PyEval_CallObjectWithKeywords (func=0x83037dc,
arg=0x83141f4, kw=0x0) at Python/ceval.c:3283
#20 0x08141779 in PyFile_WriteObject (v=0x8398e28, f=0x83ab0dc,
flags=1) at Objects/fileobject.c:164
#21 0x08141974 in PyFile_WriteString (s=0x819a2f2 "Exception ",
f=0x83ab0dc) at Objects/fileobject.c:189
#22 0x080c473c in PyErr_WriteUnraisable (obj=0x81fbd78) at
Python/errors.c:696
#23 0xb7f9612f in CallExternalTimer (pObj=0x83a7aa8)
at /home/haypo/prog/py3k/Modules/_lsprof.c:135
#24 0xb7f96984 in Stop (pObj=0x83a7aa8, self=0x826c6d8,
entry=0x826ec80) at /home/haypo/prog/py3k/Modules/_lsprof.c:337
#25 0xb7f96c60 in ptrace_leave_call (self=0x83a7aa8, key=0x81cb150)
at /home/haypo/prog/py3k/Modules/_lsprof.c:420
#26 0xb7f96d5c in profiler_callback (self=0x83a7aa8, frame=0x835a0b4,
what=6, arg=0x83ab92c) at /home/haypo/prog/py3k/Modules/_lsprof.c:471
#27 0x080b28cb in call_trace (func=0xb7f96c85 <profiler_callback>,
obj=0x83a7aa8, frame=0x835a0b4, what=6, arg=0x83ab92c)
at Python/ceval.c:3090
#28 0x080b35da in call_function (pp_stack=0xbfbf9d74, oparg=1) at
Python/ceval.c:3403
#29 0x080ae7a6 in PyEval_EvalFrameEx (f=0x835a0b4, throwflag=0) at
Python/ceval.c:2205
ceval hook: Python/ceval.3403:
PCALL(PCALL_CFUNCTION);
if (flags & (METH_NOARGS | METH_O)) {
...
} else {
PyObject *callargs;
callargs = load_args(pp_stack, na);
READ_TIMESTAMP(*pintr0);
C_TRACE(x, PyCFunction_Call(func,callargs,NULL)); <= **here**
READ_TIMESTAMP(*pintr1);
Py_XDECREF(callargs);
}
----------
components: Library (Lib)
messages: 71537
nosy: haypo
severity: normal
status: open
title: possible deadlock in IO library (Lib/io.py)
type: crash
versions: Python 3.0
_______________________________________
Python tracker <[EMAIL PROTECTED]>
<http://bugs.python.org/issue3618>
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