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/*
* Copyright (c) 2010 Twisted Matrix Laboratories.
* See LICENSE for details.
*/
#include <signal.h>
#include <errno.h>
#include "Python.h"
static int sigchld_pipe_fd = -1;
static void got_signal(int sig) {
int saved_errno = errno;
ssize_t ignored_result;
/* write() errors are unhandled. If the buffer is full, we don't
* care. What about other errors? */
ignored_result = write(sigchld_pipe_fd, "x", 1);
errno = saved_errno;
}
PyDoc_STRVAR(install_sigchld_handler_doc, "\
install_sigchld_handler(fd)\n\
\n\
Installs a SIGCHLD handler which will write a byte to the given fd\n\
whenever a SIGCHLD occurs. This is done in C code because the python\n\
signal handling system is not reliable, and additionally cannot\n\
specify SA_RESTART.\n\
\n\
Please ensure fd is in non-blocking mode.\n\
");
static PyObject *
install_sigchld_handler(PyObject *self, PyObject *args) {
int fd, old_fd;
struct sigaction sa;
if (!PyArg_ParseTuple(args, "i:install_sigchld_handler", &fd)) {
return NULL;
}
old_fd = sigchld_pipe_fd;
sigchld_pipe_fd = fd;
if (fd == -1) {
sa.sa_handler = SIG_DFL;
} else {
sa.sa_handler = got_signal;
sa.sa_flags = SA_RESTART;
/* mask all signals so I don't worry about EINTR from the write. */
sigfillset(&sa.sa_mask);
}
if (sigaction(SIGCHLD, &sa, 0) != 0) {
sigchld_pipe_fd = old_fd;
return PyErr_SetFromErrno(PyExc_OSError);
}
return PyLong_FromLong(old_fd);
}
PyDoc_STRVAR(is_default_handler_doc, "\
Return 1 if the SIGCHLD handler is SIG_DFL, 0 otherwise.\n\
");
static PyObject *
is_default_handler(PyObject *self, PyObject *args) {
/*
* This implementation is necessary since the install_sigchld_handler
* function above bypasses the Python signal handler installation API, so
* CPython doesn't notice that the handler has changed and signal.getsignal
* won't return an accurate result.
*/
struct sigaction sa;
if (sigaction(SIGCHLD, NULL, &sa) != 0) {
return PyErr_SetFromErrno(PyExc_OSError);
}
return PyLong_FromLong(sa.sa_handler == SIG_DFL);
}
static PyMethodDef sigchld_methods[] = {
{"installHandler", install_sigchld_handler, METH_VARARGS,
install_sigchld_handler_doc},
{"isDefaultHandler", is_default_handler, METH_NOARGS,
is_default_handler_doc},
/* sentinel */
{NULL, NULL, 0, NULL}
};
static const char _sigchld_doc[] = "\n\
This module contains an API for receiving SIGCHLD via a file descriptor.\n\
";
PyMODINIT_FUNC
init_sigchld(void) {
/* Create the module and add the functions */
Py_InitModule3(
"twisted.internet._sigchld", sigchld_methods, _sigchld_doc);
}
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