bpo-20104: Add flag capabilities to posix_spawn (GH-6693)

Implement the "attributes objects" parameter of `os.posix_spawn` to complete the implementation and fully cover the underlying API.

Doc/library/os.rst

@@ -3394,7 +3394,9 @@ written in Python, such as a mail server's external command delivery program.
    subprocesses.
 
 
-.. function:: posix_spawn(path, argv, env, file_actions=None)
+.. function:: posix_spawn(path, argv, env, file_actions=None, /, *, \
+                          setpgroup=None, resetids=False, setsigmask=(), \
+                          setsigdef=(), scheduler=None)
 
    Wraps the :c:func:`posix_spawn` C library API for use from Python.
 
@@ -3432,6 +3434,36 @@ written in Python, such as a mail server's external command delivery program.
    :c:func:`posix_spawn_file_actions_adddup2` API calls used to prepare
    for the :c:func:`posix_spawn` call itself.
 
+   The *setpgroup* argument will set the process group of the child to the value
+   specified. If the value specified is 0, the child's process group ID will be
+   made the same as its process ID. If the value of *setpgroup* is not set, the
+   child will inherit the parent's process group ID. This argument corresponds
+   to the C library :c:data:`POSIX_SPAWN_SETPGROUP` flag.
+
+   If the *resetids* argument is ``True`` it will reset the effective UID and
+   GID of the child to the real UID and GID of the parent process. If the
+   argument is ``False``, then the child retains the effective UID and GID of
+   the parent. In either case, if the set-user-ID and set-group-ID permission
+   bits are enabled on the executable file, their effect will override the
+   setting of the effective UID and GID. This argument corresponds to the C
+   library :c:data:`POSIX_SPAWN_RESETIDS` flag.
+
+   The *setsigmask* argument will set the signal mask to the signal set
+   specified. If the parameter is not used, then the child inherits the
+   parent's signal mask. This argument corresponds to the C library
+   :c:data:`POSIX_SPAWN_SETSIGMASK` flag.
+
+   The *sigdef* argument will reset the disposition of all signals in the set
+   specified. This argument corresponds to the C library
+   :c:data:`POSIX_SPAWN_SETSIGDEF` flag.
+
+   The *scheduler* argument must be a tuple containing the (optional) scheduler
+   policy and an instance of :class:`sched_param` with the scheduler parameters.
+   A value of ``None`` in the place of the scheduler policy indicates that is
+   not being provided. This argument is a combination of the C library
+   :c:data:`POSIX_SPAWN_SETSCHEDPARAM` and :c:data:`POSIX_SPAWN_SETSCHEDULER`
+   flags.
+
    .. versionadded:: 3.7
 
 

Lib/test/test_posix.py

@@ -8,6 +8,7 @@ posix = support.import_module('posix')
 
 import errno
 import sys
+import signal
 import time
 import os
 import platform
@@ -16,6 +17,7 @@ import stat
 import tempfile
 import unittest
 import warnings
+import textwrap
 
 _DUMMY_SYMLINK = os.path.join(tempfile.gettempdir(),
                               support.TESTFN + '-dummy-symlink')
@@ -1540,6 +1542,147 @@ class TestPosixSpawn(unittest.TestCase):
         )
         self.assertEqual(os.waitpid(pid, 0), (pid, 0))
 
+    def test_resetids_explicit_default(self):
+        pid = posix.posix_spawn(
+            sys.executable,
+            [sys.executable, '-c', 'pass'],
+            os.environ,
+            resetids=False
+        )
+        self.assertEqual(os.waitpid(pid, 0), (pid, 0))
+
+    def test_resetids(self):
+        pid = posix.posix_spawn(
+            sys.executable,
+            [sys.executable, '-c', 'pass'],
+            os.environ,
+            resetids=True
+        )
+        self.assertEqual(os.waitpid(pid, 0), (pid, 0))
+
+    def test_resetids_wrong_type(self):
+        with self.assertRaises(TypeError):
+            posix.posix_spawn(sys.executable,
+                              [sys.executable, "-c", "pass"],
+                              os.environ, resetids=None)
+
+    def test_setpgroup(self):
+        pid = posix.posix_spawn(
+            sys.executable,
+            [sys.executable, '-c', 'pass'],
+            os.environ,
+            setpgroup=os.getpgrp()
+        )
+        self.assertEqual(os.waitpid(pid, 0), (pid, 0))
+
+    def test_setpgroup_wrong_type(self):
+        with self.assertRaises(TypeError):
+            posix.posix_spawn(sys.executable,
+                              [sys.executable, "-c", "pass"],
+                              os.environ, setpgroup="023")
+
+    @unittest.skipUnless(hasattr(signal, 'pthread_sigmask'),
+                           'need signal.pthread_sigmask()')
+    def test_setsigmask(self):
+        code = textwrap.dedent("""\
+            import _testcapi, signal
+            _testcapi.raise_signal(signal.SIGUSR1)""")
+
+        pid = posix.posix_spawn(
+            sys.executable,
+            [sys.executable, '-c', code],
+            os.environ,
+            setsigmask=[signal.SIGUSR1]
+        )
+        self.assertEqual(os.waitpid(pid, 0), (pid, 0))
+
+    def test_setsigmask_wrong_type(self):
+        with self.assertRaises(TypeError):
+            posix.posix_spawn(sys.executable,
+                              [sys.executable, "-c", "pass"],
+                              os.environ, setsigmask=34)
+        with self.assertRaises(TypeError):
+            posix.posix_spawn(sys.executable,
+                              [sys.executable, "-c", "pass"],
+                              os.environ, setsigmask=["j"])
+        with self.assertRaises(ValueError):
+            posix.posix_spawn(sys.executable,
+                              [sys.executable, "-c", "pass"],
+                              os.environ, setsigmask=[signal.NSIG,
+                                                      signal.NSIG+1])
+
+    @unittest.skipUnless(hasattr(signal, 'pthread_sigmask'),
+                         'need signal.pthread_sigmask()')
+    def test_setsigdef(self):
+        original_handler = signal.signal(signal.SIGUSR1, signal.SIG_IGN)
+        code = textwrap.dedent("""\
+            import _testcapi, signal
+            _testcapi.raise_signal(signal.SIGUSR1)""")
+        try:
+            pid = posix.posix_spawn(
+                sys.executable,
+                [sys.executable, '-c', code],
+                os.environ,
+                setsigdef=[signal.SIGUSR1]
+            )
+        finally:
+            signal.signal(signal.SIGUSR1, original_handler)
+
+        pid2, status = os.waitpid(pid, 0)
+        self.assertEqual(pid2, pid)
+        self.assertTrue(os.WIFSIGNALED(status), status)
+        self.assertEqual(os.WTERMSIG(status), signal.SIGUSR1)
+
+    def test_setsigdef_wrong_type(self):
+        with self.assertRaises(TypeError):
+            posix.posix_spawn(sys.executable,
+                              [sys.executable, "-c", "pass"],
+                              os.environ, setsigdef=34)
+        with self.assertRaises(TypeError):
+            posix.posix_spawn(sys.executable,
+                              [sys.executable, "-c", "pass"],
+                              os.environ, setsigdef=["j"])
+        with self.assertRaises(ValueError):
+            posix.posix_spawn(sys.executable,
+                              [sys.executable, "-c", "pass"],
+                              os.environ, setsigdef=[signal.NSIG, signal.NSIG+1])
+
+    @unittest.skipUnless(hasattr(posix, 'sched_setscheduler'), "can't change scheduler")
+    def test_setscheduler_only_param(self):
+        policy = os.sched_getscheduler(0)
+        priority = os.sched_get_priority_min(policy)
+        code = textwrap.dedent(f"""\
+            import os
+            if os.sched_getscheduler(0) != {policy}:
+                os.exit(101)
+            if os.sched_getparam(0).sched_priority != {priority}:
+                os.exit(102)""")
+        pid = posix.posix_spawn(
+            sys.executable,
+            [sys.executable, '-c', code],
+            os.environ,
+            scheduler=(None, os.sched_param(priority))
+        )
+        self.assertEqual(os.waitpid(pid, 0), (pid, 0))
+
+    @unittest.skipUnless(hasattr(posix, 'sched_setscheduler'), "can't change scheduler")
+    def test_setscheduler_with_policy(self):
+        policy = os.sched_getscheduler(0)
+        priority = os.sched_get_priority_min(policy)
+        code = textwrap.dedent(f"""\
+            import os
+            if os.sched_getscheduler(0) != {policy}:
+                os.exit(101)
+            if os.sched_getparam(0).sched_priority != {priority}:
+                os.exit(102)""")
+        pid = posix.posix_spawn(
+            sys.executable,
+            [sys.executable, '-c', code],
+            os.environ,
+            scheduler=(policy, os.sched_param(priority))
+        )
+        self.assertEqual(os.waitpid(pid, 0), (pid, 0))
+
     def test_multiple_file_actions(self):
         file_actions = [
             (os.POSIX_SPAWN_OPEN, 3, os.path.realpath(__file__), os.O_RDONLY, 0),

Misc/NEWS.d/next/Core and Builtins/2018-05-05-23-26-58.bpo-20104.tDBciE.rst

+Added support for the `setpgroup`, `resetids`, `setsigmask`, `setsigdef` and
+`scheduler` parameters of `posix_spawn`. Patch by Pablo Galindo.

Modules/clinic/posixmodule.c.h

@@ -1730,7 +1730,9 @@ exit:
 #if defined(HAVE_POSIX_SPAWN)
 
 PyDoc_STRVAR(os_posix_spawn__doc__,
-"posix_spawn($module, path, argv, env, file_actions=None, /)\n"
+"posix_spawn($module, path, argv, env, file_actions=None, /, *,\n"
+"            setpgroup=None, resetids=False, setsigmask=(),\n"
+"            setsigdef=(), scheduler=None)\n"
 "--\n"
 "\n"
 "Execute the program specified by path in a new process.\n"
@@ -1742,29 +1744,48 @@ PyDoc_STRVAR(os_posix_spawn__doc__,
 "  env\n"
 "    Dictionary of strings mapping to strings.\n"
 "  file_actions\n"
-"    A sequence of file action tuples.");
+"    A sequence of file action tuples.\n"
+"  setpgroup\n"
+"    The pgroup to use with the POSIX_SPAWN_SETPGROUP flag.\n"
+"  resetids\n"
+"    If the value is `True` the POSIX_SPAWN_RESETIDS will be activated.\n"
+"  setsigmask\n"
+"    The sigmask to use with the POSIX_SPAWN_SETSIGMASK flag.\n"
+"  setsigdef\n"
+"    The sigmask to use with the POSIX_SPAWN_SETSIGDEF flag.\n"
+"  scheduler\n"
+"    A tuple with the scheduler policy (optional) and parameters.");
 
 #define OS_POSIX_SPAWN_METHODDEF    \
-    {"posix_spawn", (PyCFunction)os_posix_spawn, METH_FASTCALL, os_posix_spawn__doc__},
+    {"posix_spawn", (PyCFunction)os_posix_spawn, METH_FASTCALL|METH_KEYWORDS, os_posix_spawn__doc__},
 
 static PyObject *
 os_posix_spawn_impl(PyObject *module, path_t *path, PyObject *argv,
-                    PyObject *env, PyObject *file_actions);
+                    PyObject *env, PyObject *file_actions,
+                    PyObject *setpgroup, int resetids, PyObject *setsigmask,
+                    PyObject *setsigdef, PyObject *scheduler);
 
 static PyObject *
-os_posix_spawn(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
+os_posix_spawn(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
 {
     PyObject *return_value = NULL;
+    static const char * const _keywords[] = {"", "", "", "", "setpgroup", "resetids", "setsigmask", "setsigdef", "scheduler", NULL};
+    static _PyArg_Parser _parser = {"O&OO|O$OiOOO:posix_spawn", _keywords, 0};
     path_t path = PATH_T_INITIALIZE("posix_spawn", "path", 0, 0);
     PyObject *argv;
     PyObject *env;
     PyObject *file_actions = Py_None;
+    PyObject *setpgroup = NULL;
+    int resetids = 0;
+    PyObject *setsigmask = NULL;
+    PyObject *setsigdef = NULL;
+    PyObject *scheduler = NULL;
 
-    if (!_PyArg_ParseStack(args, nargs, "O&OO|O:posix_spawn",
-        path_converter, &path, &argv, &env, &file_actions)) {
+    if (!_PyArg_ParseStackAndKeywords(args, nargs, kwnames, &_parser,
+        path_converter, &path, &argv, &env, &file_actions, &setpgroup, &resetids, &setsigmask, &setsigdef, &scheduler)) {
         goto exit;
     }
-    return_value = os_posix_spawn_impl(module, &path, argv, env, file_actions);
+    return_value = os_posix_spawn_impl(module, &path, argv, env, file_actions, setpgroup, resetids, setsigmask, setsigdef, scheduler);
 
 exit:
     /* Cleanup for path */
@@ -6627,4 +6648,4 @@ exit:
 #ifndef OS_GETRANDOM_METHODDEF
     #define OS_GETRANDOM_METHODDEF
 #endif /* !defined(OS_GETRANDOM_METHODDEF) */
-/*[clinic end generated code: output=47fb6a3e88cba6d9 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=ef78384ae88712e1 input=a9049054013a1b77]*/

Modules/posixmodule.c

@@ -5177,6 +5177,114 @@ enum posix_spawn_file_actions_identifier {
     POSIX_SPAWN_DUP2
 };
 
+static int
+convert_sched_param(PyObject *param, struct sched_param *res);
+
+static int
+parse_posix_spawn_flags(PyObject *setpgroup, int resetids, PyObject *setsigmask,
+                        PyObject *setsigdef, PyObject *scheduler,
+                        posix_spawnattr_t *attrp)
+{
+    long all_flags = 0;
+
+    errno = posix_spawnattr_init(attrp);
+    if (errno) {
+        posix_error();
+        return -1;
+    }
+
+    if (setpgroup) {
+        pid_t pgid = PyLong_AsPid(setpgroup);
+        if (pgid == (pid_t)-1 && PyErr_Occurred()) {
+            goto fail;
+        }
+        errno = posix_spawnattr_setpgroup(attrp, pgid);
+        if (errno) {
+            posix_error();
+            goto fail;
+        }
+        all_flags |= POSIX_SPAWN_SETPGROUP;
+    }
+
+    if (resetids) {
+        all_flags |= POSIX_SPAWN_RESETIDS;
+    }
+
+   if (setsigmask) {
+        sigset_t set;
+        if (!_Py_Sigset_Converter(setsigmask, &set)) {
+            goto fail;
+        }
+        errno = posix_spawnattr_setsigmask(attrp, &set);
+        if (errno) {
+            posix_error();
+            goto fail;
+        }
+        all_flags |= POSIX_SPAWN_SETSIGMASK;
+    }
+
+    if (setsigdef) {
+        sigset_t set;
+        if (!_Py_Sigset_Converter(setsigdef, &set)) {
+            goto fail;
+        }
+        errno = posix_spawnattr_setsigdefault(attrp, &set);
+        if (errno) {
+            posix_error();
+            goto fail;
+        }
+        all_flags |= POSIX_SPAWN_SETSIGDEF;
+    }
+
+    if (scheduler) {
+#ifdef POSIX_SPAWN_SETSCHEDULER
+        PyObject *py_schedpolicy;
+        struct sched_param schedparam;
+
+        if (!PyArg_ParseTuple(scheduler, "OO&"
+                        ";A scheduler tuple must have two elements",
+                        &py_schedpolicy, convert_sched_param, &schedparam)) {
+            goto fail;
+        }
+        if (py_schedpolicy != Py_None) {
+            int schedpolicy = _PyLong_AsInt(py_schedpolicy);
+
+            if (schedpolicy == -1 && PyErr_Occurred()) {
+                goto fail;
+            }
+            errno = posix_spawnattr_setschedpolicy(attrp, schedpolicy);
+            if (errno) {
+                posix_error();
+                goto fail;
+            }
+            all_flags |= POSIX_SPAWN_SETSCHEDULER;
+        }
+        errno = posix_spawnattr_setschedparam(attrp, &schedparam);
+        if (errno) {
+            posix_error();
+            goto fail;
+        }
+        all_flags |= POSIX_SPAWN_SETSCHEDPARAM;
+#else
+        PyErr_SetString(PyExc_NotImplementedError,
+                "The scheduler option is not supported in this system.");
+        goto fail;
+#endif
+    }
+
+    errno = posix_spawnattr_setflags(attrp, all_flags);
+    if (errno) {
+        posix_error();
+        goto fail;
+    }
+
+    return 0;
+
+fail:
+    (void)posix_spawnattr_destroy(attrp);
+    return -1;
+}
+
 static int
 parse_file_actions(PyObject *file_actions,
                    posix_spawn_file_actions_t *file_actionsp,
@@ -5277,6 +5385,7 @@ parse_file_actions(PyObject *file_actions,
         }
         Py_DECREF(file_action);
     }
+
     Py_DECREF(seq);
     return 0;
 
@@ -5299,19 +5408,33 @@ os.posix_spawn
     file_actions: object = None
         A sequence of file action tuples.
     /
-
+    *
+    setpgroup: object = NULL
+        The pgroup to use with the POSIX_SPAWN_SETPGROUP flag.
+    resetids: bool(accept={int}) = False
+        If the value is `True` the POSIX_SPAWN_RESETIDS will be activated.
+    setsigmask: object(c_default='NULL') = ()
+        The sigmask to use with the POSIX_SPAWN_SETSIGMASK flag.
+    setsigdef: object(c_default='NULL') = ()
+        The sigmask to use with the POSIX_SPAWN_SETSIGDEF flag.
+    scheduler: object = NULL
+        A tuple with the scheduler policy (optional) and parameters.
 Execute the program specified by path in a new process.
 [clinic start generated code]*/
 
 static PyObject *
 os_posix_spawn_impl(PyObject *module, path_t *path, PyObject *argv,
-                    PyObject *env, PyObject *file_actions)
-/*[clinic end generated code: output=d023521f541c709c input=a3db1021d33230dc]*/
+                    PyObject *env, PyObject *file_actions,
+                    PyObject *setpgroup, int resetids, PyObject *setsigmask,
+                    PyObject *setsigdef, PyObject *scheduler)
+/*[clinic end generated code: output=45dfa4c515d09f2c input=2d7a7578430a90f0]*/
 {
     EXECV_CHAR **argvlist = NULL;
     EXECV_CHAR **envlist = NULL;
     posix_spawn_file_actions_t file_actions_buf;
     posix_spawn_file_actions_t *file_actionsp = NULL;
+    posix_spawnattr_t attr;
+    posix_spawnattr_t *attrp = NULL;
     Py_ssize_t argc, envc;
     PyObject *result = NULL;
     PyObject *temp_buffer = NULL;
@@ -5373,9 +5496,15 @@ os_posix_spawn_impl(PyObject *module, path_t *path, PyObject *argv,
         file_actionsp = &file_actions_buf;
     }
 
+    if (parse_posix_spawn_flags(setpgroup, resetids, setsigmask,
+                                setsigdef, scheduler, &attr)) {
+        goto exit;
+    }
+    attrp = &attr;
+
     _Py_BEGIN_SUPPRESS_IPH
     err_code = posix_spawn(&pid, path->narrow,
-                           file_actionsp, NULL, argvlist, envlist);
+                           file_actionsp, attrp, argvlist, envlist);
     _Py_END_SUPPRESS_IPH
     if (err_code) {
         errno = err_code;
@@ -5388,6 +5517,9 @@ exit:
     if (file_actionsp) {
         (void)posix_spawn_file_actions_destroy(file_actionsp);
     }
+    if (attrp) {
+        (void)posix_spawnattr_destroy(attrp);
+    }
     if (envlist) {
         free_string_array(envlist, envc);
     }