bpo-41001: Add os.eventfd() (#20930)

Co-authored-by: Kyle Stanley <aeros167@gmail.com>

2 files changed, 232 insertions, 1 deletions

diff --git a/Modules/clinic/posixmodule.c.h b/Modules/clinic/posixmodule.c.h
index df680d5738..f5826e3681 100644
--- a/Modules/clinic/posixmodule.c.h
+++ b/Modules/clinic/posixmodule.c.h
@@ -7620,6 +7620,134 @@ exit:
 
 #endif /* defined(HAVE_MEMFD_CREATE) */
 
+#if defined(HAVE_EVENTFD)
+
+PyDoc_STRVAR(os_eventfd__doc__,
+"eventfd($module, /, initval, flags=EFD_CLOEXEC)\n"
+"--\n"
+"\n"
+"Creates and returns an event notification file descriptor.");
+
+#define OS_EVENTFD_METHODDEF    \
+    {"eventfd", (PyCFunction)(void(*)(void))os_eventfd, METH_FASTCALL|METH_KEYWORDS, os_eventfd__doc__},
+
+static PyObject *
+os_eventfd_impl(PyObject *module, unsigned int initval, int flags);
+
+static PyObject *
+os_eventfd(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
+{
+    PyObject *return_value = NULL;
+    static const char * const _keywords[] = {"initval", "flags", NULL};
+    static _PyArg_Parser _parser = {NULL, _keywords, "eventfd", 0};
+    PyObject *argsbuf[2];
+    Py_ssize_t noptargs = nargs + (kwnames ? PyTuple_GET_SIZE(kwnames) : 0) - 1;
+    unsigned int initval;
+    int flags = EFD_CLOEXEC;
+
+    args = _PyArg_UnpackKeywords(args, nargs, NULL, kwnames, &_parser, 1, 2, 0, argsbuf);
+    if (!args) {
+        goto exit;
+    }
+    if (!_PyLong_UnsignedInt_Converter(args[0], &initval)) {
+        goto exit;
+    }
+    if (!noptargs) {
+        goto skip_optional_pos;
+    }
+    flags = _PyLong_AsInt(args[1]);
+    if (flags == -1 && PyErr_Occurred()) {
+        goto exit;
+    }
+skip_optional_pos:
+    return_value = os_eventfd_impl(module, initval, flags);
+
+exit:
+    return return_value;
+}
+
+#endif /* defined(HAVE_EVENTFD) */
+
+#if defined(HAVE_EVENTFD)
+
+PyDoc_STRVAR(os_eventfd_read__doc__,
+"eventfd_read($module, /, fd)\n"
+"--\n"
+"\n"
+"Read eventfd value");
+
+#define OS_EVENTFD_READ_METHODDEF    \
+    {"eventfd_read", (PyCFunction)(void(*)(void))os_eventfd_read, METH_FASTCALL|METH_KEYWORDS, os_eventfd_read__doc__},
+
+static PyObject *
+os_eventfd_read_impl(PyObject *module, int fd);
+
+static PyObject *
+os_eventfd_read(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
+{
+    PyObject *return_value = NULL;
+    static const char * const _keywords[] = {"fd", NULL};
+    static _PyArg_Parser _parser = {NULL, _keywords, "eventfd_read", 0};
+    PyObject *argsbuf[1];
+    int fd;
+
+    args = _PyArg_UnpackKeywords(args, nargs, NULL, kwnames, &_parser, 1, 1, 0, argsbuf);
+    if (!args) {
+        goto exit;
+    }
+    if (!_PyLong_FileDescriptor_Converter(args[0], &fd)) {
+        goto exit;
+    }
+    return_value = os_eventfd_read_impl(module, fd);
+
+exit:
+    return return_value;
+}
+
+#endif /* defined(HAVE_EVENTFD) */
+
+#if defined(HAVE_EVENTFD)
+
+PyDoc_STRVAR(os_eventfd_write__doc__,
+"eventfd_write($module, /, fd, value)\n"
+"--\n"
+"\n"
+"Write eventfd value.");
+
+#define OS_EVENTFD_WRITE_METHODDEF    \
+    {"eventfd_write", (PyCFunction)(void(*)(void))os_eventfd_write, METH_FASTCALL|METH_KEYWORDS, os_eventfd_write__doc__},
+
+static PyObject *
+os_eventfd_write_impl(PyObject *module, int fd, unsigned long long value);
+
+static PyObject *
+os_eventfd_write(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
+{
+    PyObject *return_value = NULL;
+    static const char * const _keywords[] = {"fd", "value", NULL};
+    static _PyArg_Parser _parser = {NULL, _keywords, "eventfd_write", 0};
+    PyObject *argsbuf[2];
+    int fd;
+    unsigned long long value;
+
+    args = _PyArg_UnpackKeywords(args, nargs, NULL, kwnames, &_parser, 2, 2, 0, argsbuf);
+    if (!args) {
+        goto exit;
+    }
+    if (!_PyLong_FileDescriptor_Converter(args[0], &fd)) {
+        goto exit;
+    }
+    if (!_PyLong_UnsignedLongLong_Converter(args[1], &value)) {
+        goto exit;
+    }
+    return_value = os_eventfd_write_impl(module, fd, value);
+
+exit:
+    return return_value;
+}
+
+#endif /* defined(HAVE_EVENTFD) */
+
 #if (defined(TERMSIZE_USE_CONIO) || defined(TERMSIZE_USE_IOCTL))
 
 PyDoc_STRVAR(os_get_terminal_size__doc__,
@@ -8884,6 +9012,18 @@ exit:
     #define OS_MEMFD_CREATE_METHODDEF
 #endif /* !defined(OS_MEMFD_CREATE_METHODDEF) */
 
+#ifndef OS_EVENTFD_METHODDEF
+    #define OS_EVENTFD_METHODDEF
+#endif /* !defined(OS_EVENTFD_METHODDEF) */
+
+#ifndef OS_EVENTFD_READ_METHODDEF
+    #define OS_EVENTFD_READ_METHODDEF
+#endif /* !defined(OS_EVENTFD_READ_METHODDEF) */
+
+#ifndef OS_EVENTFD_WRITE_METHODDEF
+    #define OS_EVENTFD_WRITE_METHODDEF
+#endif /* !defined(OS_EVENTFD_WRITE_METHODDEF) */
+
 #ifndef OS_GET_TERMINAL_SIZE_METHODDEF
     #define OS_GET_TERMINAL_SIZE_METHODDEF
 #endif /* !defined(OS_GET_TERMINAL_SIZE_METHODDEF) */
@@ -8919,4 +9059,4 @@ exit:
 #ifndef OS_WAITSTATUS_TO_EXITCODE_METHODDEF
     #define OS_WAITSTATUS_TO_EXITCODE_METHODDEF
 #endif /* !defined(OS_WAITSTATUS_TO_EXITCODE_METHODDEF) */
-/*[clinic end generated code: output=936f33448cd66ccb input=a9049054013a1b77]*/
+/*[clinic end generated code: output=49b7ed768242ef7c input=a9049054013a1b77]*/
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 6b51d8a848..0764453f41 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -518,6 +518,11 @@ extern char        *ctermid_r(char *);
 #  include <linux/memfd.h>
 #endif
 
+/* eventfd() */
+#ifdef HAVE_SYS_EVENTFD_H
+#  include <sys/eventfd.h>
+#endif
+
 #ifdef _Py_MEMORY_SANITIZER
 #  include <sanitizer/msan_interface.h>
 #endif
@@ -12859,6 +12864,79 @@ os_memfd_create_impl(PyObject *module, PyObject *name, unsigned int flags)
 }
 #endif
 
+#ifdef HAVE_EVENTFD
+/*[clinic input]
+os.eventfd
+
+    initval: unsigned_int
+    flags: int(c_default="EFD_CLOEXEC") = EFD_CLOEXEC
+
+Creates and returns an event notification file descriptor.
+[clinic start generated code]*/
+
+static PyObject *
+os_eventfd_impl(PyObject *module, unsigned int initval, int flags)
+/*[clinic end generated code: output=ce9c9bbd1446f2de input=66203e3c50c4028b]*/
+
+{
+    /* initval is limited to uint32_t, internal counter is uint64_t */
+    int fd;
+    Py_BEGIN_ALLOW_THREADS
+    fd = eventfd(initval, flags);
+    Py_END_ALLOW_THREADS
+    if (fd == -1) {
+        return PyErr_SetFromErrno(PyExc_OSError);
+    }
+    return PyLong_FromLong(fd);
+}
+
+/*[clinic input]
+os.eventfd_read
+
+    fd: fildes
+
+Read eventfd value
+[clinic start generated code]*/
+
+static PyObject *
+os_eventfd_read_impl(PyObject *module, int fd)
+/*[clinic end generated code: output=8f2c7b59a3521fd1 input=110f8b57fa596afe]*/
+{
+    eventfd_t value;
+    int result;
+    Py_BEGIN_ALLOW_THREADS
+    result = eventfd_read(fd, &value);
+    Py_END_ALLOW_THREADS
+    if (result == -1) {
+        return PyErr_SetFromErrno(PyExc_OSError);
+    }
+    return PyLong_FromUnsignedLongLong(value);
+}
+
+/*[clinic input]
+os.eventfd_write
+
+    fd: fildes
+    value: unsigned_long_long
+
+Write eventfd value.
+[clinic start generated code]*/
+
+static PyObject *
+os_eventfd_write_impl(PyObject *module, int fd, unsigned long long value)
+/*[clinic end generated code: output=bebd9040bbf987f5 input=156de8555be5a949]*/
+{
+    int result;
+    Py_BEGIN_ALLOW_THREADS
+    result = eventfd_write(fd, value);
+    Py_END_ALLOW_THREADS
+    if (result == -1) {
+        return PyErr_SetFromErrno(PyExc_OSError);
+    }
+    Py_RETURN_NONE;
+}
+#endif  /* HAVE_EVENTFD */
+
 /* Terminal size querying */
 
 PyDoc_STRVAR(TerminalSize_docstring,
@@ -14619,6 +14697,9 @@ static PyMethodDef posix_methods[] = {
     OS_FSPATH_METHODDEF
     OS_GETRANDOM_METHODDEF
     OS_MEMFD_CREATE_METHODDEF
+    OS_EVENTFD_METHODDEF
+    OS_EVENTFD_READ_METHODDEF
+    OS_EVENTFD_WRITE_METHODDEF
     OS__ADD_DLL_DIRECTORY_METHODDEF
     OS__REMOVE_DLL_DIRECTORY_METHODDEF
     OS_WAITSTATUS_TO_EXITCODE_METHODDEF
@@ -15127,6 +15208,12 @@ all_ins(PyObject *m)
 #ifdef MFD_HUGE_16GB
     if (PyModule_AddIntMacro(m, MFD_HUGE_16GB)) return -1;
 #endif
+#endif /* HAVE_MEMFD_CREATE */
+
+#ifdef HAVE_EVENTFD
+    if (PyModule_AddIntMacro(m, EFD_CLOEXEC)) return -1;
+    if (PyModule_AddIntMacro(m, EFD_NONBLOCK)) return -1;
+    if (PyModule_AddIntMacro(m, EFD_SEMAPHORE)) return -1;
 #endif
 
 #if defined(__APPLE__)
@@ -15220,6 +15307,10 @@ static const struct have_function {
     int (*probe)(void);
 } have_functions[] = {
 
+#ifdef HAVE_EVENTFD
+    {"HAVE_EVENTFD", NULL},
+#endif
+
 #ifdef HAVE_FACCESSAT
     { "HAVE_FACCESSAT", probe_faccessat },
 #endif