Bloody signal handling (in embedded Python code)

[Marcin Krol]

Hello everyone,

And now for something completely different: signal handling sometimes
works, sometimes it doesn't.

When I embed following code, it works:


count = 0

def test():
global count
while True:
count += 1
if (count % 100000 == 0):
print count

if __name__ == "__main__":
test()

It nicely does what signal handler function tells it to do and exits.


However, when I embed this code, it segfaults on receiving the signal:


import time

def test():
time.sleep(1)
print "success"
time.sleep(90)

if __name__ == "__main__":
test()


Does it have something to do with the fact that the program receiving
the signal sleeps?

The C code of segfaulting program:

#include <Python.h>
#include <stdio.h>
#include <stdlib.h>
#include <syslog.h>
#include <unistd.h>
#include <signal.h>

void userbreak(int sig)
{
Py_Finalize();
printf("Interrupted..\n");
exit(sig);
}

void terminaterun(int sig)
{
Py_Finalize();
printf("Received SIGTERM. Terminating.\n");
exit(sig);
}

int main(int argc, char **argv)
{
Py_Initialize();
PyObject *pyCode, *mainmodule, *maindict;
mainmodule = PyImport_AddModule("__main__");
maindict = PyModule_GetDict(mainmodule);
unsigned int size = 326;

unsigned char python_code[] = { 0x63,0x00,0x00,
0x00,0x00,0x00,0x00,0x00,0x00,0x02,0x00,0x00,0x00,
0x40,0x00,0x00,0x00,0x73,0x2E,0x00,0x00,0x00,0x64,
0x00,0x00,0x6B,0x00,0x00,0x5A,0x00,0x00,0x64,0x01,
0x00,0x84,0x00,0x00,0x5A,0x01,0x00,0x65,0x02,0x00,
0x64,0x02,0x00,0x6A,0x02,0x00,0x6F,0x0B,0x00,0x01,
0x65,0x01,0x00,0x83,0x00,0x00,0x01,0x6E,0x01,0x00,
0x01,0x64,0x00,0x00,0x53,0x28,0x03,0x00,0x00,0x00,
0x4E,0x63,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
0x02,0x00,0x00,0x00,0x43,0x00,0x00,0x00,0x73,0x23,
0x00,0x00,0x00,0x74,0x00,0x00,0x69,0x01,0x00,0x64,
0x01,0x00,0x83,0x01,0x00,0x01,0x64,0x02,0x00,0x47,
0x48,0x74,0x00,0x00,0x69,0x01,0x00,0x64,0x03,0x00,
0x83,0x01,0x00,0x01,0x64,0x00,0x00,0x53,0x28,0x04,
0x00,0x00,0x00,0x4E,0x69,0x01,0x00,0x00,0x00,0x74,
0x07,0x00,0x00,0x00,0x73,0x75,0x63,0x63,0x65,0x73,
0x73,0x69,0x5A,0x00,0x00,0x00,0x28,0x02,0x00,0x00,
0x00,0x74,0x04,0x00,0x00,0x00,0x74,0x69,0x6D,0x65,
0x74,0x05,0x00,0x00,0x00,0x73,0x6C,0x65,0x65,0x70,
0x28,0x00,0x00,0x00,0x00,0x28,0x00,0x00,0x00,0x00,
0x28,0x00,0x00,0x00,0x00,0x74,0x07,0x00,0x00,0x00,
0x74,0x65,0x73,0x74,0x2E,0x70,0x79,0x74,0x04,0x00,
0x00,0x00,0x74,0x65,0x73,0x74,0x05,0x00,0x00,0x00,
0x73,0x06,0x00,0x00,0x00,0x00,0x01,0x0D,0x01,0x05,
0x01,0x74,0x08,0x00,0x00,0x00,0x5F,0x5F,0x6D,0x61,
0x69,0x6E,0x5F,0x5F,0x28,0x03,0x00,0x00,0x00,0x52,
0x01,0x00,0x00,0x00,0x52,0x04,0x00,0x00,0x00,0x74,
0x08,0x00,0x00,0x00,0x5F,0x5F,0x6E,0x61,0x6D,0x65,
0x5F,0x5F,0x28,0x02,0x00,0x00,0x00,0x52,0x04,0x00,
0x00,0x00,0x52,0x01,0x00,0x00,0x00,0x28,0x00,0x00,
0x00,0x00,0x28,0x00,0x00,0x00,0x00,0x52,0x03,0x00,
0x00,0x00,0x74,0x01,0x00,0x00,0x00,0x3F,0x03,0x00,
0x00,0x00,0x73,0x06,0x00,0x00,0x00,0x09,0x02,0x09,
0x05,0x0D,0x01 };

pyCode = PyMarshal_ReadObjectFromString((PyObject *)
python_code, size);

(void) signal(SIGINT, userbreak);
(void) signal(SIGTERM, terminaterun);
PyEval_EvalCode(pyCode, maindict, maindict);

Py_Finalize();

}