gh-59705: Export threading.Thread() names to the OS

Include/pythread.h

@@ -31,6 +31,12 @@ PyAPI_FUNC(unsigned long) PyThread_get_thread_ident(void);
 PyAPI_FUNC(unsigned long) PyThread_get_thread_native_id(void);
 #endif
 
+#if defined(__APPLE__) || defined(__linux__) || defined(__FreeBSD__) || \
+    defined(__OpenBSD__) || defined(__NetBSD__)
+#define PY_HAVE_SET_THREAD_NAME
+PyAPI_FUNC(int) PyThread_set_thread_name(const char *);
+#endif
+
 PyAPI_FUNC(PyThread_type_lock) PyThread_allocate_lock(void);
 PyAPI_FUNC(void) PyThread_free_lock(PyThread_type_lock);
 PyAPI_FUNC(int) PyThread_acquire_lock(PyThread_type_lock, int);

Lib/threading.py

@@ -41,6 +41,11 @@
     __all__.append('get_native_id')
 except AttributeError:
     _HAVE_THREAD_NATIVE_ID = False
+try:
+    _set_thread_name = _thread._set_thread_name
+    _HAVE_SET_THREAD_NAME = True
+except AttributeError:
+    _HAVE_SET_THREAD_NAME = False
 ThreadError = _thread.error
 try:
     _CRLock = _thread.RLock
@@ -924,6 +929,8 @@ def _bootstrap_inner(self):
             self._set_tstate_lock()
             if _HAVE_THREAD_NATIVE_ID:
                 self._set_native_id()
+            if _HAVE_SET_THREAD_NAME:
+                _set_thread_name(self.name)
             self._started.set()
             with _active_limbo_lock:
                 _active[self._ident] = self

Misc/NEWS.d/next/Library/2019-07-03-17-31-07.bpo-15500.Ey3JkG.rst

@@ -0,0 +1 @@
+Export :class:`threading.Thread` names to the OS.

Modules/_threadmodule.c

@@ -1094,6 +1094,30 @@ function returns; the return value is ignored.  The thread will also exit\n\
 when the function raises an unhandled exception; a stack trace will be\n\
 printed unless the exception is SystemExit.\n");
 
+#ifdef PY_HAVE_SET_THREAD_NAME
+/*[clinic input]
+_thread._set_thread_name
+
+    name: object(converter="PyUnicode_FSConverter")
+    /
+
+Set the name of the current thread.
+[clinic start generated code]*/
+
+static PyObject *
+_thread__set_thread_name_impl(PyObject *module, PyObject *name)
+/*[clinic end generated code: output=72d978d5c53e2762 input=8c46f838fc1040c2]*/
+{
+    if (PyThread_set_thread_name(PyBytes_AS_STRING(name))) {
+        Py_DECREF(name);
+        PyErr_SetString(ThreadError, "setting the thread name failed");
+        return NULL;
+    }
+    Py_DECREF(name);
+    Py_RETURN_NONE;
+}
+#endif
+
 static PyObject *
 thread_PyThread_exit_thread(PyObject *self, PyObject *Py_UNUSED(ignored))
 {
@@ -1495,6 +1519,7 @@ static PyMethodDef thread_methods[] = {
     {"_excepthook",              thread_excepthook,
      METH_O, excepthook_doc},
     _THREAD__IS_MAIN_INTERPRETER_METHODDEF
+    _THREAD__SET_THREAD_NAME_METHODDEF
     {NULL,                      NULL}           /* sentinel */
 };
 

Python/thread_pthread.h

@@ -17,6 +17,7 @@
 #elif defined(__FreeBSD__)
 #   include <pthread_np.h>      /* pthread_getthreadid_np() */
 #elif defined(__OpenBSD__)
+#   include <pthread_np.h>
 #   include <unistd.h>          /* getthrid() */
 #elif defined(_AIX)
 #   include <sys/thread.h>      /* thread_self() */
@@ -343,6 +344,37 @@ PyThread_get_thread_native_id(void)
 }
 #endif
 
+#ifdef PY_HAVE_SET_THREAD_NAME
+int
+PyThread_set_thread_name(const char *name)
+{
+    if (!initialized) {
+        PyThread_init_thread();
+    }
+    // Truncate the string to 15 chars for pthread_setname_np().
+    char buf[16];
+    size_t len = Py_ARRAY_LENGTH(buf) - 1;
+    strncpy(buf, name, len);
+    buf[len] = '\0';
+#ifndef __APPLE__
+    unsigned long ident = PyThread_get_thread_ident();
+#endif
+    int ret = 0;
+#ifdef __APPLE__
+    // On macOS, pthread_setname_np() can only set the calling thread's name.
+    ret = pthread_setname_np(buf);
+#elif defined(__FreeBSD__) || defined(__OpenBSD__)
+    // No return value.
+    pthread_set_name_np((pthread_t)ident, buf);
+#elif defined(__NetBSD__)
+    ret = pthread_setname_np((pthread_t)ident, "%s", (void *)buf);
+#elif defined(__linux__)
+    ret = pthread_setname_np((pthread_t)ident, buf);
+#endif
+    return ret;
+}
+#endif
+
 void _Py_NO_RETURN
 PyThread_exit_thread(void)
 {