3 * Job client low-level magic
5 * (c) 2019 Mark Wooding
8 /*----- Licensing notice --------------------------------------------------*
10 * This file is part of the distorted.org.uk chroot maintenance tools.
12 * distorted-chroot is free software: you can redistribute it and/or
13 * modify it under the terms of the GNU General Public License as
14 * published by the Free Software Foundation; either version 2 of the
15 * License, or (at your option) any later version.
17 * distorted-chroot is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
20 * General Public License for more details.
22 * You should have received a copy of the GNU General Public License
23 * along with distorted-chroot. If not, write to the Free Software
24 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
28 /*----- Header files ------------------------------------------------------*/
34 #include <sys/types.h>
36 #include <sys/select.h>
39 #define PY_SSIZE_T_CLEAN
42 /*----- Static variables --------------------------------------------------*/
44 static volatile int sigfd = -1;
46 /*----- Main code ---------------------------------------------------------*/
48 static void chld(int sig)
49 { int fd = sigfd; if (fd != -1) { close(fd); sigfd = -1; } }
51 static PyObject *pymeth_jobclient(PyObject *me, PyObject *arg)
54 struct sigaction sa, oldsa;
55 sigset_t mask, oldmask;
63 /* Parse the arguments. */
64 if (!PyArg_ParseTuple(arg, "i", &fd)) goto end;
66 /* Prepare to be able to block `SIGCHLD'. */
67 sigemptyset(&mask); sigaddset(&mask, SIGCHLD);
68 if (sigprocmask(SIG_SETMASK, 0, &oldmask)) goto oserr;
70 /* Establish the signal handler. */
72 sigemptyset(&sa.sa_mask); sigaddset(&sa.sa_mask, SIGCHLD);
73 sa.sa_flags = SA_NOCLDSTOP;
74 if (sigaction(SIGCHLD, &sa, &oldsa)) goto oserr;
77 /* Establish a copy of the file descriptor. If a signal occurs, we'll
78 * clobber this descriptor: see below. If we come back here, we'll
79 * probably need to reinstate this, but check just in case: we don't want a
83 if (sigprocmask(SIG_BLOCK, &mask, 0)) goto oserr;
86 sfd = dup(fd); if (sfd == -1) goto oserr;
89 if (sigprocmask(SIG_UNBLOCK, &mask, 0)) goto oserr;
91 /* Check for child processes. If a child exit somehow failed to be
92 * spotted earlier, this is our chance to notice and do something about it.
94 kid = waitpid(-1, &st, WNOHANG);
95 if (kid == -1 && errno != ECHILD) goto oserr;
97 { rc = Py_BuildValue("(Oii)", Py_None, kid, st); goto end; }
99 /* Read from the pipe. If a child exits between the `waitpid' above and
100 * the `read' here, the signal handler will pop and close the descriptor,
101 * so `read' will report `EBADF'. If a child exits while we're waiting for
102 * a byte on the descriptor, then `read' will report `EINTR'. If anything
103 * like this happens, then we go back and try reaping children again.
105 Py_BEGIN_ALLOW_THREADS
107 n = read(sigfd, &ch, 1); if (n >= 0 || errno != EAGAIN) break;
108 FD_ZERO(&infd); FD_SET(sigfd, &infd);
109 n = select(sigfd + 1, &infd, 0, 0, 0); if (n < 0) break;
112 if (n == 1) rc = Py_BuildValue("(cOO)", ch, Py_None, Py_None);
113 else if (!n) rc = Py_BuildValue("(sOO)", "", Py_None, Py_None);
115 PyErr_SetString(PyExc_SystemError, "impossible return from read");
117 } else if (errno == EINTR || errno == EBADF) goto again;
124 /* Report a system error. */
125 PyErr_SetFromErrnoWithFilename(PyExc_OSError, 0); goto end;
128 /* Clean up and return. */
130 sigprocmask(SIG_SETMASK, &oldmask, 0);
131 sigaction(SIGCHLD, &oldsa, 0);
133 sfd = sigfd; if (sfd != -1) { close(sfd); sigfd = -1; }
137 static PyMethodDef methods[] = {
138 { "jobclient", pymeth_jobclient, METH_VARARGS,
139 "jobclient(FD) -> (TOKEN, PID, STATUS)" },
143 PyMODINIT_FUNC initjobclient(void)
144 { Py_InitModule("jobclient", methods); }
146 /*----- That's all, folks -------------------------------------------------*/