bpo-35813: Added shared_memory submodule of multiprocessing. (#11664)
Added shared_memory submodule to multiprocessing in time for first alpha with cross-platform tests soon to follow.
diff --git a/Modules/_multiprocessing/posixshmem.c b/Modules/_multiprocessing/posixshmem.c
new file mode 100644
index 0000000..7dd29f4
--- /dev/null
+++ b/Modules/_multiprocessing/posixshmem.c
@@ -0,0 +1,724 @@
+/*
+posixshmem - A Python module for accessing POSIX 1003.1b-1993 shared memory.
+
+Copyright (c) 2012, Philip Semanchuk
+Copyright (c) 2018, 2019, Davin Potts
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+ * Redistributions of source code must retain the above copyright
+ notice, this list of conditions and the following disclaimer.
+ * Redistributions in binary form must reproduce the above copyright
+ notice, this list of conditions and the following disclaimer in the
+ documentation and/or other materials provided with the distribution.
+ * Neither the name of posixshmem nor the names of its contributors may
+ be used to endorse or promote products derived from this software
+ without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY ITS CONTRIBUTORS ''AS IS'' AND ANY
+EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL Philip Semanchuk BE LIABLE FOR ANY
+DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+#define PY_SSIZE_T_CLEAN
+
+#include <Python.h>
+#include "structmember.h"
+
+#include <time.h>
+#include <sys/time.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <stdio.h>
+
+// For shared memory stuff
+#include <sys/stat.h>
+#include <sys/mman.h>
+
+/* SEM_FAILED is defined as an int in Apple's headers, and this makes the
+compiler complain when I compare it to a pointer. Python faced the same
+problem (issue 9586) and I copied their solution here.
+ref: http://bugs.python.org/issue9586
+
+Note that in /Developer/SDKs/MacOSX10.4u.sdk/usr/include/sys/semaphore.h,
+SEM_FAILED is #defined as -1 and that's apparently the definition used by
+Python when building. In /usr/include/sys/semaphore.h, it's defined
+as ((sem_t *)-1).
+*/
+#ifdef __APPLE__
+ #undef SEM_FAILED
+ #define SEM_FAILED ((sem_t *)-1)
+#endif
+
+/* POSIX says that a mode_t "shall be an integer type". To avoid the need
+for a specific get_mode function for each type, I'll just stuff the mode into
+a long and mention it in the Xxx_members list for each type.
+ref: http://www.opengroup.org/onlinepubs/000095399/basedefs/sys/types.h.html
+*/
+
+typedef struct {
+ PyObject_HEAD
+ char *name;
+ long mode;
+ int fd;
+} SharedMemory;
+
+
+// FreeBSD (and perhaps other BSDs) limit names to 14 characters. In the
+// code below, strings of this length are allocated on the stack, so
+// increase this gently or change that code to use malloc().
+#define MAX_SAFE_NAME_LENGTH 14
+
+
+/* Struct to contain an IPC object name which can be None */
+typedef struct {
+ int is_none;
+ char *name;
+} NoneableName;
+
+
+/*
+ Exceptions for this module
+*/
+
+static PyObject *pBaseException;
+static PyObject *pPermissionsException;
+static PyObject *pExistentialException;
+
+
+#ifdef POSIX_IPC_DEBUG
+#define DPRINTF(fmt, args...) fprintf(stderr, "+++ " fmt, ## args)
+#else
+#define DPRINTF(fmt, args...)
+#endif
+
+static char *
+bytes_to_c_string(PyObject* o, int lock) {
+/* Convert a bytes object to a char *. Optionally lock the buffer if it is a
+ bytes array.
+ This code swiped directly from Python 3.1's posixmodule.c by Philip S.
+ The name there is bytes2str().
+*/
+ if (PyBytes_Check(o))
+ return PyBytes_AsString(o);
+ else if (PyByteArray_Check(o)) {
+ if (lock && PyObject_GetBuffer(o, NULL, 0) < 0)
+ /* On a bytearray, this should not fail. */
+ PyErr_BadInternalCall();
+ return PyByteArray_AsString(o);
+ } else {
+ /* The FS converter should have verified that this
+ is either bytes or bytearray. */
+ Py_FatalError("bad object passed to bytes2str");
+ /* not reached. */
+ return "";
+ }
+}
+
+static void
+release_bytes(PyObject* o)
+ /* Release the lock, decref the object.
+ This code swiped directly from Python 3.1's posixmodule.c by Philip S.
+ */
+{
+ if (PyByteArray_Check(o))
+ o->ob_type->tp_as_buffer->bf_releasebuffer(NULL, 0);
+ Py_DECREF(o);
+}
+
+
+static int
+random_in_range(int min, int max) {
+ // returns a random int N such that min <= N <= max
+ int diff = (max - min) + 1;
+
+ // ref: http://www.c-faq.com/lib/randrange.html
+ return ((int)((double)rand() / ((double)RAND_MAX + 1) * diff)) + min;
+}
+
+
+static
+int create_random_name(char *name) {
+ // The random name is always lowercase so that this code will work
+ // on case-insensitive file systems. It always starts with a forward
+ // slash.
+ int length;
+ char *alphabet = "abcdefghijklmnopqrstuvwxyz";
+ int i;
+
+ // Generate a random length for the name. I subtract 1 from the
+ // MAX_SAFE_NAME_LENGTH in order to allow for the name's leading "/".
+ length = random_in_range(6, MAX_SAFE_NAME_LENGTH - 1);
+
+ name[0] = '/';
+ name[length] = '\0';
+ i = length;
+ while (--i)
+ name[i] = alphabet[random_in_range(0, 25)];
+
+ return length;
+}
+
+
+static int
+convert_name_param(PyObject *py_name_param, void *checked_name) {
+ /* Verifies that the py_name_param is either None or a string.
+ If it's a string, checked_name->name points to a PyMalloc-ed buffer
+ holding a NULL-terminated C version of the string when this function
+ concludes. The caller is responsible for releasing the buffer.
+ */
+ int rc = 0;
+ NoneableName *p_name = (NoneableName *)checked_name;
+ PyObject *py_name_as_bytes = NULL;
+ char *p_name_as_c_string = NULL;
+
+ DPRINTF("inside convert_name_param\n");
+ DPRINTF("PyBytes_Check() = %d \n", PyBytes_Check(py_name_param));
+ DPRINTF("PyString_Check() = %d \n", PyString_Check(py_name_param));
+ DPRINTF("PyUnicode_Check() = %d \n", PyUnicode_Check(py_name_param));
+
+ p_name->is_none = 0;
+
+ // The name can be None or a Python string
+ if (py_name_param == Py_None) {
+ DPRINTF("name is None\n");
+ rc = 1;
+ p_name->is_none = 1;
+ }
+ else if (PyUnicode_Check(py_name_param) || PyBytes_Check(py_name_param)) {
+ DPRINTF("name is Unicode or bytes\n");
+ // The caller passed me a Unicode string or a byte array; I need a
+ // char *. Getting from one to the other takes a couple steps.
+
+ if (PyUnicode_Check(py_name_param)) {
+ DPRINTF("name is Unicode\n");
+ // PyUnicode_FSConverter() converts the Unicode object into a
+ // bytes or a bytearray object. (Why can't it be one or the other?)
+ PyUnicode_FSConverter(py_name_param, &py_name_as_bytes);
+ }
+ else {
+ DPRINTF("name is bytes\n");
+ // Make a copy of the name param.
+ py_name_as_bytes = PyBytes_FromObject(py_name_param);
+ }
+
+ // bytes_to_c_string() returns a pointer to the buffer.
+ p_name_as_c_string = bytes_to_c_string(py_name_as_bytes, 0);
+
+ // PyMalloc memory and copy the user-supplied name to it.
+ p_name->name = (char *)PyMem_Malloc(strlen(p_name_as_c_string) + 1);
+ if (p_name->name) {
+ rc = 1;
+ strcpy(p_name->name, p_name_as_c_string);
+ }
+ else
+ PyErr_SetString(PyExc_MemoryError, "Out of memory");
+
+ // The bytes version of the name isn't useful to me, and per the
+ // documentation for PyUnicode_FSConverter(), I am responsible for
+ // releasing it when I'm done.
+ release_bytes(py_name_as_bytes);
+ }
+ else
+ PyErr_SetString(PyExc_TypeError, "Name must be None or a string");
+
+ return rc;
+}
+
+
+
+/* ===== Begin Shared Memory implementation functions ===== */
+
+static PyObject *
+shm_str(SharedMemory *self) {
+ return PyUnicode_FromString(self->name ? self->name : "(no name)");
+}
+
+static PyObject *
+shm_repr(SharedMemory *self) {
+ char mode[32];
+
+ sprintf(mode, "0%o", (int)(self->mode));
+
+ return PyUnicode_FromFormat("_posixshmem.SharedMemory(\"%s\", mode=%s)",
+ self->name, mode);
+}
+
+static PyObject *
+my_shm_unlink(const char *name) {
+ DPRINTF("unlinking shm name %s\n", name);
+ if (-1 == shm_unlink(name)) {
+ switch (errno) {
+ case EACCES:
+ PyErr_SetString(pPermissionsException, "Permission denied");
+ break;
+
+ case ENOENT:
+ PyErr_SetString(pExistentialException,
+ "No shared memory exists with the specified name");
+ break;
+
+ case ENAMETOOLONG:
+ PyErr_SetString(PyExc_ValueError, "The name is too long");
+ break;
+
+ default:
+ PyErr_SetFromErrno(PyExc_OSError);
+ break;
+ }
+
+ goto error_return;
+ }
+
+ Py_RETURN_NONE;
+
+ error_return:
+ return NULL;
+}
+
+
+static PyObject *
+SharedMemory_new(PyTypeObject *type, PyObject *args, PyObject *kwlist) {
+ SharedMemory *self;
+
+ self = (SharedMemory *)type->tp_alloc(type, 0);
+
+ return (PyObject *)self;
+}
+
+
+static int
+SharedMemory_init(SharedMemory *self, PyObject *args, PyObject *keywords) {
+ NoneableName name;
+ char temp_name[MAX_SAFE_NAME_LENGTH + 1];
+ unsigned int flags = 0;
+ unsigned long size = 0;
+ int read_only = 0;
+ static char *keyword_list[ ] = {"name", "flags", "mode", "size", "read_only", NULL};
+
+ // First things first -- initialize the self struct.
+ self->name = NULL;
+ self->fd = 0;
+ self->mode = 0600;
+
+ if (!PyArg_ParseTupleAndKeywords(args, keywords, "O&|Iiki", keyword_list,
+ &convert_name_param, &name, &flags,
+ &(self->mode), &size, &read_only))
+ goto error_return;
+
+ if ( !(flags & O_CREAT) && (flags & O_EXCL) ) {
+ PyErr_SetString(PyExc_ValueError,
+ "O_EXCL must be combined with O_CREAT");
+ goto error_return;
+ }
+
+ if (name.is_none && ((flags & O_EXCL) != O_EXCL)) {
+ PyErr_SetString(PyExc_ValueError,
+ "Name can only be None if O_EXCL is set");
+ goto error_return;
+ }
+
+ flags |= (read_only ? O_RDONLY : O_RDWR);
+
+ if (name.is_none) {
+ // (name == None) ==> generate a name for the caller
+ do {
+ errno = 0;
+ create_random_name(temp_name);
+
+ DPRINTF("calling shm_open, name=%s, flags=0x%x, mode=0%o\n",
+ temp_name, flags, (int)self->mode);
+ self->fd = shm_open(temp_name, flags, (mode_t)self->mode);
+
+ } while ( (-1 == self->fd) && (EEXIST == errno) );
+
+ // PyMalloc memory and copy the randomly-generated name to it.
+ self->name = (char *)PyMem_Malloc(strlen(temp_name) + 1);
+ if (self->name)
+ strcpy(self->name, temp_name);
+ else {
+ PyErr_SetString(PyExc_MemoryError, "Out of memory");
+ goto error_return;
+ }
+ }
+ else {
+ // (name != None) ==> use name supplied by the caller. It was
+ // already converted to C by convert_name_param().
+ self->name = name.name;
+
+ DPRINTF("calling shm_open, name=%s, flags=0x%x, mode=0%o\n",
+ self->name, flags, (int)self->mode);
+ self->fd = shm_open(self->name, flags, (mode_t)self->mode);
+ }
+
+ DPRINTF("shm fd = %d\n", self->fd);
+
+ if (-1 == self->fd) {
+ self->fd = 0;
+ switch (errno) {
+ case EACCES:
+ PyErr_Format(pPermissionsException,
+ "No permission to %s this segment",
+ (flags & O_TRUNC) ? "truncate" : "access"
+ );
+ break;
+
+ case EEXIST:
+ PyErr_SetString(pExistentialException,
+ "Shared memory with the specified name already exists");
+ break;
+
+ case ENOENT:
+ PyErr_SetString(pExistentialException,
+ "No shared memory exists with the specified name");
+ break;
+
+ case EINVAL:
+ PyErr_SetString(PyExc_ValueError, "Invalid parameter(s)");
+ break;
+
+ case EMFILE:
+ PyErr_SetString(PyExc_OSError,
+ "This process already has the maximum number of files open");
+ break;
+
+ case ENFILE:
+ PyErr_SetString(PyExc_OSError,
+ "The system limit on the total number of open files has been reached");
+ break;
+
+ case ENAMETOOLONG:
+ PyErr_SetString(PyExc_ValueError,
+ "The name is too long");
+ break;
+
+ default:
+ PyErr_SetFromErrno(PyExc_OSError);
+ break;
+ }
+
+ goto error_return;
+ }
+ else {
+ if (size) {
+ DPRINTF("calling ftruncate, fd = %d, size = %ld\n", self->fd, size);
+ if (-1 == ftruncate(self->fd, (off_t)size)) {
+ // The code below will raise a Python error. Since that error
+ // is raised during __init__(), it will look to the caller
+ // as if object creation failed entirely. Here I clean up
+ // the system object I just created.
+ close(self->fd);
+ shm_unlink(self->name);
+
+ // ftruncate can return a ton of different errors, but most
+ // are not relevant or are extremely unlikely.
+ switch (errno) {
+ case EINVAL:
+ PyErr_SetString(PyExc_ValueError,
+ "The size is invalid or the memory is read-only");
+ break;
+
+ case EFBIG:
+ PyErr_SetString(PyExc_ValueError,
+ "The size is too large");
+ break;
+
+ case EROFS:
+ case EACCES:
+ PyErr_SetString(pPermissionsException,
+ "The memory is read-only");
+ break;
+
+ default:
+ PyErr_SetFromErrno(PyExc_OSError);
+ break;
+ }
+
+ goto error_return;
+ }
+ }
+ }
+
+ return 0;
+
+ error_return:
+ return -1;
+}
+
+
+static void SharedMemory_dealloc(SharedMemory *self) {
+ DPRINTF("dealloc\n");
+ PyMem_Free(self->name);
+ self->name = NULL;
+
+ Py_TYPE(self)->tp_free((PyObject*)self);
+}
+
+
+PyObject *
+SharedMemory_getsize(SharedMemory *self, void *closure) {
+ struct stat fileinfo;
+ off_t size = -1;
+
+ if (0 == fstat(self->fd, &fileinfo))
+ size = fileinfo.st_size;
+ else {
+ switch (errno) {
+ case EBADF:
+ case EINVAL:
+ PyErr_SetString(pExistentialException,
+ "The segment does not exist");
+ break;
+
+ default:
+ PyErr_SetFromErrno(PyExc_OSError);
+ break;
+ }
+
+ goto error_return;
+ }
+
+ return Py_BuildValue("k", (unsigned long)size);
+
+ error_return:
+ return NULL;
+}
+
+
+PyObject *
+SharedMemory_close_fd(SharedMemory *self) {
+ if (self->fd) {
+ if (-1 == close(self->fd)) {
+ switch (errno) {
+ case EBADF:
+ PyErr_SetString(PyExc_ValueError,
+ "The file descriptor is invalid");
+ break;
+
+ default:
+ PyErr_SetFromErrno(PyExc_OSError);
+ break;
+ }
+
+ goto error_return;
+ }
+ }
+
+ Py_RETURN_NONE;
+
+ error_return:
+ return NULL;
+}
+
+
+PyObject *
+SharedMemory_unlink(SharedMemory *self) {
+ return my_shm_unlink(self->name);
+}
+
+
+/* ===== End Shared Memory functions ===== */
+
+
+/*
+ *
+ * Shared memory meta stuff for describing myself to Python
+ *
+ */
+
+
+static PyMemberDef SharedMemory_members[] = {
+ { "name",
+ T_STRING,
+ offsetof(SharedMemory, name),
+ READONLY,
+ "The name specified in the constructor"
+ },
+ { "fd",
+ T_INT,
+ offsetof(SharedMemory, fd),
+ READONLY,
+ "Shared memory segment file descriptor"
+ },
+ { "mode",
+ T_LONG,
+ offsetof(SharedMemory, mode),
+ READONLY,
+ "The mode specified in the constructor"
+ },
+ {NULL} /* Sentinel */
+};
+
+
+static PyMethodDef SharedMemory_methods[] = {
+ { "close_fd",
+ (PyCFunction)SharedMemory_close_fd,
+ METH_NOARGS,
+ "Closes the file descriptor associated with the shared memory."
+ },
+ { "unlink",
+ (PyCFunction)SharedMemory_unlink,
+ METH_NOARGS,
+ "Unlink (remove) the shared memory."
+ },
+ {NULL, NULL, 0, NULL} /* Sentinel */
+};
+
+
+static PyGetSetDef SharedMemory_getseters[] = {
+ // size is read-only
+ { "size",
+ (getter)SharedMemory_getsize,
+ (setter)NULL,
+ "size",
+ NULL
+ },
+ {NULL} /* Sentinel */
+};
+
+
+static PyTypeObject SharedMemoryType = {
+ PyVarObject_HEAD_INIT(NULL, 0)
+ "_posixshmem._PosixSharedMemory", // tp_name
+ sizeof(SharedMemory), // tp_basicsize
+ 0, // tp_itemsize
+ (destructor) SharedMemory_dealloc, // tp_dealloc
+ 0, // tp_print
+ 0, // tp_getattr
+ 0, // tp_setattr
+ 0, // tp_compare
+ (reprfunc) shm_repr, // tp_repr
+ 0, // tp_as_number
+ 0, // tp_as_sequence
+ 0, // tp_as_mapping
+ 0, // tp_hash
+ 0, // tp_call
+ (reprfunc) shm_str, // tp_str
+ 0, // tp_getattro
+ 0, // tp_setattro
+ 0, // tp_as_buffer
+ Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
+ // tp_flags
+ "POSIX shared memory object", // tp_doc
+ 0, // tp_traverse
+ 0, // tp_clear
+ 0, // tp_richcompare
+ 0, // tp_weaklistoffset
+ 0, // tp_iter
+ 0, // tp_iternext
+ SharedMemory_methods, // tp_methods
+ SharedMemory_members, // tp_members
+ SharedMemory_getseters, // tp_getset
+ 0, // tp_base
+ 0, // tp_dict
+ 0, // tp_descr_get
+ 0, // tp_descr_set
+ 0, // tp_dictoffset
+ (initproc) SharedMemory_init, // tp_init
+ 0, // tp_alloc
+ (newfunc) SharedMemory_new, // tp_new
+ 0, // tp_free
+ 0, // tp_is_gc
+ 0 // tp_bases
+};
+
+
+/*
+ *
+ * Module-level functions & meta stuff
+ *
+ */
+
+static PyObject *
+posixshmem_unlink_shared_memory(PyObject *self, PyObject *args) {
+ const char *name;
+
+ if (!PyArg_ParseTuple(args, "s", &name))
+ return NULL;
+ else
+ return my_shm_unlink(name);
+}
+
+
+static PyMethodDef module_methods[ ] = {
+ { "unlink_shared_memory",
+ (PyCFunction)posixshmem_unlink_shared_memory,
+ METH_VARARGS,
+ "Unlink shared memory"
+ },
+ {NULL} /* Sentinel */
+};
+
+
+static struct PyModuleDef this_module = {
+ PyModuleDef_HEAD_INIT, // m_base
+ "_posixshmem", // m_name
+ "POSIX shared memory module", // m_doc
+ -1, // m_size (space allocated for module globals)
+ module_methods, // m_methods
+ NULL, // m_reload
+ NULL, // m_traverse
+ NULL, // m_clear
+ NULL // m_free
+};
+
+/* Module init function */
+PyMODINIT_FUNC
+PyInit__posixshmem(void) {
+ PyObject *module;
+ PyObject *module_dict;
+
+ // I call this in case I'm asked to create any random names.
+ srand((unsigned int)time(NULL));
+
+ module = PyModule_Create(&this_module);
+
+ if (!module)
+ goto error_return;
+
+ if (PyType_Ready(&SharedMemoryType) < 0)
+ goto error_return;
+
+ Py_INCREF(&SharedMemoryType);
+ PyModule_AddObject(module, "_PosixSharedMemory", (PyObject *)&SharedMemoryType);
+
+
+ PyModule_AddStringConstant(module, "__copyright__", "Copyright 2012 Philip Semanchuk, 2018-2019 Davin Potts");
+
+ PyModule_AddIntConstant(module, "O_CREAT", O_CREAT);
+ PyModule_AddIntConstant(module, "O_EXCL", O_EXCL);
+ PyModule_AddIntConstant(module, "O_CREX", O_CREAT | O_EXCL);
+ PyModule_AddIntConstant(module, "O_TRUNC", O_TRUNC);
+
+ if (!(module_dict = PyModule_GetDict(module)))
+ goto error_return;
+
+ // Exceptions
+ if (!(pBaseException = PyErr_NewException("_posixshmem.Error", NULL, NULL)))
+ goto error_return;
+ else
+ PyDict_SetItemString(module_dict, "Error", pBaseException);
+
+ if (!(pPermissionsException = PyErr_NewException("_posixshmem.PermissionsError", pBaseException, NULL)))
+ goto error_return;
+ else
+ PyDict_SetItemString(module_dict, "PermissionsError", pPermissionsException);
+
+ if (!(pExistentialException = PyErr_NewException("_posixshmem.ExistentialError", pBaseException, NULL)))
+ goto error_return;
+ else
+ PyDict_SetItemString(module_dict, "ExistentialError", pExistentialException);
+
+ return module;
+
+ error_return:
+ return NULL;
+}