From 7d00c1f0a473296fa6cee0353d7381523a32c0af Mon Sep 17 00:00:00 2001
From: Henrik Holst <henrik.holst@millistream.com>
Date: Wed, 3 May 2023 07:42:50 +0200
Subject: [PATCH] added cpucorectl.c

Added a utility to enable and disable cpu cores (aka core parking) since this requires root privileges
---
 util/cpucorectl.c | 140 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 140 insertions(+)
 create mode 100644 util/cpucorectl.c

diff --git a/util/cpucorectl.c b/util/cpucorectl.c
new file mode 100644
index 0000000..4579d17
--- /dev/null
+++ b/util/cpucorectl.c
@@ -0,0 +1,140 @@
+/*
+
+Copyright (c) 2017-2019, Feral Interactive
+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 Feral Interactive 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 THE COPYRIGHT HOLDERS AND 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 THE COPYRIGHT OWNER OR CONTRIBUTORS 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 _GNU_SOURCE
+
+#include <sched.h>
+#include <unistd.h>
+#include <linux/limits.h>
+
+#include "common-cpu.h"
+#include "common-logging.h"
+
+static int write_state (char *path, int state)
+{
+	FILE *f = fopen(path, "w");
+
+	if (!f) {
+		LOG_ERROR("Couldn't open file at %s (%s)\n", path, strerror(errno));
+		return 0;
+	}
+
+	if (putc (state, f) == EOF) {
+		LOG_ERROR("Couldn't write to file at %s (%s)\n", path, strerror(errno));
+		fclose (f);
+		return 0;
+	}
+
+	fclose (f);
+	return 1;
+}
+
+static void log_state (const int state, const long first, const long last)
+{
+	if (state == '0') {
+		if (first == last)
+			LOG_MSG("parked core %ld\n", first);
+		else
+			LOG_MSG("parked cores %ld - %ld\n", first, last);
+	} else {
+		if (first == last)
+			LOG_MSG("unparked core %ld\n", first);
+		else
+			LOG_MSG("unparked cores %ld - %ld\n", first, last);
+	}
+}
+
+static int set_state (char *cpulist, int state)
+{
+	char path[PATH_MAX];
+	long from, to;
+	char *list = cpulist;
+
+	long first = -1, last = -1;
+
+	while ((list = parse_cpulist(list, &from, &to))) {
+		for (long cpu = from; cpu < to + 1; cpu++) {
+			if (snprintf(path, PATH_MAX, "/sys/devices/system/cpu/cpu%ld/online", cpu) < 0) {
+				LOG_ERROR("snprintf failed, will not apply cpu core parking!\n");
+				return 0;
+			}
+
+			if (!write_state (path, state)) {
+				/* on some systems one cannot park core #0 */
+				if (cpu != 0) {
+					if (state == '0') {
+						LOG_ERROR("unable to park core #%ld, will not apply cpu core parking!\n", cpu);
+						return -1;
+					}
+
+					LOG_ERROR("unable to unpark core #%ld\n", cpu);
+				}
+			} else {
+				if (first == -1) {
+					first = cpu;
+					last = cpu;
+				} else if (last + 1 == cpu) {
+					last = cpu;
+				} else {
+					log_state (state, first, last);
+					first = cpu;
+					last = cpu;
+				}
+			}
+		}
+	}
+
+	if (first != -1)
+		log_state (state, first, last);
+
+	return 1;
+}
+
+int main(int argc, char *argv[])
+{
+	if (geteuid() != 0) {
+		LOG_ERROR("This program must be run as root\n");
+		return EXIT_FAILURE;
+	}
+
+	if (argc == 3 && strncmp(argv[1], "online", 6) == 0) {
+		if (!set_state (argv[2], '1'))
+			return EXIT_FAILURE;
+	} else if (argc == 3 && strncmp(argv[1], "offline", 7) == 0) {
+		if (!set_state (argv[2], '0'))
+			return EXIT_FAILURE;
+	} else {
+		fprintf(stderr, "usage: cpucorectl [online]|[offline] VALUE]\n");
+		return EXIT_FAILURE;
+	}
+
+	return EXIT_SUCCESS;
+}