[PATCH 2 of 4] osutil: implement setprocname to set process title

[Jun Wu]

# HG changeset patch
# User Jun Wu <quark at fb.com>
# Date 1470846674 -3600
#      Wed Aug 10 17:31:14 2016 +0100
# Node ID 6913c4d46efa50511191c3c310882602d07cc305
# Parent  4485f6b4073cf2e22d8a8afaddb9c86eea2a019a
# Available At https://bitbucket.org/quark-zju/hg-draft
#              hg pull https://bitbucket.org/quark-zju/hg-draft -r 6913c4d46efa
osutil: implement setprocname to set process title

Use prctl (Linux) or setproctitle (FreeBSD) to implement the feature.
It is useful for forked command servers - to show what it is doing.

diff --git a/mercurial/osutil.c b/mercurial/osutil.c
--- a/mercurial/osutil.c
+++ b/mercurial/osutil.c
@@ -31,6 +31,10 @@
 #include <sys/vnode.h>
 #endif
 
+#ifdef HAVE_PRCTL
+#include <sys/prctl.h>
+#endif
+
 #include "util.h"
 
 /* some platforms lack the PATH_MAX definition (eg. GNU/Hurd) */
@@ -719,6 +723,24 @@ bail:
 }
 
 #endif /* CMSG_LEN */
+
+#if defined(HAVE_SETPROCTITLE) || (defined(PR_SET_NAME) && defined(HAVE_PRCTL))
+static PyObject *setprocname(PyObject *self, PyObject *args)
+{
+	const char *name = NULL;
+	if (!PyArg_ParseTuple(args, "s", &name))
+		return NULL;
+
+#ifdef HAVE_SETPROCTITLE
+	setproctitle("%s", name);
+#else
+	prctl(PR_SET_NAME, name, NULL, NULL);
+#endif
+
+	Py_RETURN_NONE;
+}
+#endif
+
 #endif /* ndef _WIN32 */
 
 static PyObject *listdir(PyObject *self, PyObject *args, PyObject *kwargs)
@@ -891,7 +913,11 @@ static PyMethodDef methods[] = {
 	{"recvfds", (PyCFunction)recvfds, METH_VARARGS,
 	 "receive list of file descriptors via socket\n"},
 #endif
+#if defined(HAVE_SETPROCTITLE) || (defined(PR_SET_NAME) && defined(HAVE_PRCTL))
+	{"setprocname", (PyCFunction)setprocname, METH_VARARGS,
+	 "set process title\n"},
 #endif
+#endif /* ndef _WIN32 */
 #ifdef __APPLE__
 	{
 		"isgui", (PyCFunction)isgui, METH_NOARGS,