crash (SEGV) in Py_EndInterpreter() in multithreaded program

[Gernot Hillier]

Hi!

I experience a 80% reproducable SIGSEGV in a multithreaded app I wrote using 
different embedded sub interpreters in its threads.

I have a C++ class (PClass) which encapsulates the sub-interpreters somehow 
- it creates a new one in its constructor and deletes it in the destructor 
(see below).

When 2 objects of this class are destroyed at nearly the same time thus 
resulting in subsequent calls to Py_EndInterpreter(), I get the following 
SIGSEGV in most cases:

> gdb application core.31889
[...]
Program terminated with signal 11, Segmentation fault.
[...]
Reading symbols from /lib/ld-linux.so.2...done.
Loaded symbols for /lib/ld-linux.so.2
Reading symbols from /usr/local/lib/python2.2/lib-dynload/time.so...done.
Loaded symbols for /usr/local/lib/python2.2/lib-dynload/time.so
#0  0x08078763 in class_dealloc (op=0x81a8624) at Objects/classobject.c:169
169             _PyObject_GC_UNTRACK(op);
(gdb) bt
#0  0x08078763 in class_dealloc (op=0x81a8624) at Objects/classobject.c:169
#1  0x080daefa in PyThreadState_Clear (tstate=0x816b7f0) at 
Python/pystate.c:190
#2  0x080dab89 in PyInterpreterState_Clear (interp=0x81427e8) at 
Python/pystate.c:77
#3  0x080dce1e in Py_EndInterpreter (tstate=0x816b7f0) at 
Python/pythonrun.c:381
#4  0x0805c287 in ~PClass (this=0x81421d0) at pclass.cpp:123


When the 2nd object is destroyed some seconds later, everything seems to be 
fine. It only crashes when the 2 objects are deleted within a short period 
of time.

I've tried this with the SuSE RPMs of Python 2.2.1 and a self-built 
Python-2.2.2 with the same result. :-(

I've absolutely no clue what goes wrong here. I would appreciate any 
suggestion where to have a look. Perhaps some of you have an idea... TIA!!

Here's a very short snippet of the python related code in my class:

// Constructor, initializes Python sub-interpreter
PClass::PClass() 
{
        PyEval_AcquireLock();
        py_state=Py_NewInterpreter();
        PyEval_SaveThread();
}

// destructor, kills the Python sub-interpreter
PClass::~PClass()
{
        PyEval_RestoreThread(py_state); 
        Py_EndInterpreter(py_state);
        py_state=NULL;
        PyEval_ReleaseLock(); // release lock
}

// thread code, runs Python function 
void
PClass::run()
{
        PyEval_RestoreThread(py_state); 
        PyObject_CallFunction(...) 
        PyEval_SaveThread();
}

-- 
Ciao,

Gernot