--- /dev/null
+//po4a: entry man manual
+////
+coresched(1) manpage
+////
+= coresched(1)
+:doctype: manpage
+:man manual: User Commands
+:man source: util-linux {release-version}
+:page-layout: base
+:command: coresched
+:colon: :
+:copyright: ©
+
+== NAME
+
+coresched - manage core scheduling cookies for tasks
+
+== SYNOPSIS
+
+*{command}* [*get*] [*-s* _pid_]
+
+*{command}* *new* [*-t* _type_] *-d* _pid_
+
+*{command}* *new* [*-t* _type_] \-- _command_ [_argument_...]
+
+*{command}* *copy* [*-s* _pid_] [*-t* _type_] *-d* _pid_
+
+*{command}* *copy* [*-s* _pid_] [*-t* _type_] \-- _command_ [_argument_...]
+
+== DESCRIPTION
+The *{command}* command is used to retrieve or modify the core scheduling cookies of a running process given its _pid_, or to spawn a new _command_ with core scheduling cookies.
+
+Core scheduling permits the definition of groups of tasks that are allowed to share a physical core.
+This is done by assigning a cookie to each task.
+Only tasks have the same cookie are allowed to be scheduled on the same physical core.
+
+It is possible to either assign a new random cookie to a task, or copy a cookie from another task. It is not possible to choose the value of the cookie.
+
+== FUNCTIONS
+*get*::
+Retrieve the core scheduling cookie of the PID specified in *-s*.
+If *-s* is omitted, it will get the cookie of the current *{command}* process.
+
+*new*::
+Assign a new cookie to an existing PID specified in *-d*, or execute _command_ with a new cookie.
+
+*copy*::
+Copy the cookie from an existing PID (*-s*) to another PID (*-d*), or execute _command_ with that cookie.
+If *-s* is omitted, it will get the cookie of the current *{command}* process.
+
+If no function is specified, it will run the *get* function.
+
+== OPTIONS
+*-s*, *--source* _PID_::
+Which _PID_ to get the cookie from.
+If this option is omitted, it will get the cookie from the current *{command}* process.
+
+*-d*, *--dest* _PID_::
+Which _PID_ to modify the cookie of.
+
+*-t*, *--dest-type* _TYPE_::
+The type of the PID whose cookie will be modified. This can be one of three values:
+- *pid*, or process ID
+- *tgid*, or thread group ID (default value)
+- *pgid*, or process group ID
+
+*-v*, *--verbose*::
+Show extra information when modifying cookies of tasks.
+
+*-h*, *--help*::
+Display help text and exit.
+
+*-V*, *--version*::
+Print version and exit.
+
+== EXAMPLES
+Get the core scheduling cookie of the {command} task itself, usually inherited from its parent{colon}::
+*{command} get*
+
+Get the core scheduling cookie of a task with PID _123_{colon}::
+*{command} get -s* _123_
+
+Give a task with PID _123_ a new core scheduling cookie{colon}::
+*{command} new -d* _123_
+
+Spawn a new task with a new core scheduling cookie{colon}::
+*{command} new* \-- _command_ [_argument_...]
+
+Copy the cookie from the current {command} process another task with pid _456_{colon}::
+*{command} copy -d* _456_
+
+Copy the cookie from a task with pid _123_ to another task with pid _456_{colon}::
+*{command} copy -s* _123_ *-d* _456_
+
+Copy the cookie from a task with pid _123_ to a new task _command_{colon}::
+*{command} copy -s* _123_ \-- _command_ [_argument_...]
+
+Copy the cookie from a task with pid _123_ to the process group ID _456_{colon}::
+*{command} copy -s* _123_ *-t* _pgid_ *-d* _456_
+
+== PERMISSIONS
+Retrieving or modifying the core scheduling cookie of a process requires *PTRACE_MODE_READ_REALCREDS* ptrace access to that process.
+See the section "Ptrace access mode checking" in *ptrace*(2) for more information.
+
+== RETURN VALUE
+On success, *{command}* returns 0.
+If *{command}* fails, it will print an error and return 1.
+
+If a _command_ is being executed, the return value of *{command}* will be the return value of _command_.
+
+== NOTES
+*{command}* requires core scheduling support in the kernel.
+This can be enabled via the *CONFIG_SCHED_CORE* kernel config option.
+
+== AUTHORS
+mailto:thijs@raymakers.nl[Thijs Raymakers],
+mailto:pauld@redhat.com[Phil Auld]
+
+== COPYRIGHT
+
+Copyright {copyright} 2024 Thijs Raymakers and Phil Auld. This is free software licensed under the EUPL.
+
+== SEE ALSO
+*chrt*(1),
+*nice*(1),
+*renice*(1),
+*taskset*(1),
+*ptrace*(2),
+*sched*(7)
+
+The Linux kernel source files _Documentation/admin-guide/hw-vuln/core-scheduling.rst_
+
+include::man-common/bugreports.adoc[]
+
+include::man-common/footer.adoc[]
+
+ifdef::translation[]
+include::man-common/translation.adoc[]
+endif::[]
--- /dev/null
+/**
+ * SPDX-License-Identifier: EUPL-1.2
+ *
+ * coresched.c - manage core scheduling cookies for tasks
+ *
+ * Copyright (C) 2024 Thijs Raymakers, Phil Auld
+ * Licensed under the EUPL v1.2
+ */
+
+#include <getopt.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <sys/prctl.h>
+#include <unistd.h>
+
+#include "c.h"
+#include "closestream.h"
+#include "nls.h"
+#include "strutils.h"
+
+// These definitions might not be defined in the header files, even if the
+// prctl interface in the kernel accepts them as valid.
+#ifndef PR_SCHED_CORE
+ #define PR_SCHED_CORE 62
+#endif
+#ifndef PR_SCHED_CORE_GET
+ #define PR_SCHED_CORE_GET 0
+#endif
+#ifndef PR_SCHED_CORE_CREATE
+ #define PR_SCHED_CORE_CREATE 1
+#endif
+#ifndef PR_SCHED_CORE_SHARE_TO
+ #define PR_SCHED_CORE_SHARE_TO 2
+#endif
+#ifndef PR_SCHED_CORE_SHARE_FROM
+ #define PR_SCHED_CORE_SHARE_FROM 3
+#endif
+#ifndef PR_SCHED_CORE_SCOPE_THREAD
+ #define PR_SCHED_CORE_SCOPE_THREAD 0
+#endif
+#ifndef PR_SCHED_CORE_SCOPE_THREAD_GROUP
+ #define PR_SCHED_CORE_SCOPE_THREAD_GROUP 1
+#endif
+#ifndef PR_SCHED_CORE_SCOPE_PROCESS_GROUP
+ #define PR_SCHED_CORE_SCOPE_PROCESS_GROUP 2
+#endif
+
+typedef int sched_core_scope;
+typedef unsigned long long sched_core_cookie;
+typedef enum {
+ SCHED_CORE_CMD_GET,
+ SCHED_CORE_CMD_NEW,
+ SCHED_CORE_CMD_COPY,
+} sched_core_cmd;
+
+struct args {
+ pid_t src;
+ pid_t dest;
+ sched_core_scope type;
+ sched_core_cmd cmd;
+ int exec_argv_offset;
+};
+
+static bool sched_core_verbose = false;
+
+static void __attribute__((__noreturn__)) usage(void)
+{
+ fputs(USAGE_HEADER, stdout);
+ fprintf(stdout, _(" %s [get] [--source <PID>]\n"),
+ program_invocation_short_name);
+ fprintf(stdout, _(" %s new [-t <TYPE>] --dest <PID>\n"),
+ program_invocation_short_name);
+ fprintf(stdout, _(" %s new [-t <TYPE>] -- PROGRAM [ARGS...]\n"),
+ program_invocation_short_name);
+ fprintf(stdout,
+ _(" %s copy [--source <PID>] [-t <TYPE>] --dest <PID>\n"),
+ program_invocation_short_name);
+ fprintf(stdout,
+ _(" %s copy [--source <PID>] [-t <TYPE>] -- PROGRAM [ARGS...]\n"),
+ program_invocation_short_name);
+
+ fputs(USAGE_SEPARATOR, stdout);
+ fputsln(_("Manage core scheduling cookies for tasks."), stdout);
+
+ fputs(USAGE_FUNCTIONS, stdout);
+ fputsln(_(" get retrieve the core scheduling cookie of a PID"),
+ stdout);
+ fputsln(_(" new assign a new core scheduling cookie to an existing\n"
+ " PID or execute a program with a new cookie"),
+ stdout);
+ fputsln(_(" copy copy the core scheduling cookie from an existing PID\n"
+ " to another PID, or execute a program with that\n"
+ " copied cookie"),
+ stdout);
+
+ fputs(USAGE_OPTIONS, stdout);
+ fprintf(stdout,
+ _(" -s, --source <PID> which PID to get the cookie from\n"
+ " If omitted, it is the PID of %s itself\n"),
+ program_invocation_short_name);
+ fputsln(_(" -d, --dest <PID> which PID to modify the cookie of\n"),
+ stdout);
+ fputsln(_(" -t, --dest-type <TYPE> type of the destination PID, or the type of the PID\n"
+ " when a new core scheduling cookie is created.\n"
+ " Can be one of the following: pid, tgid or pgid.\n"
+ " The default is tgid."),
+ stdout);
+ fputs(USAGE_SEPARATOR, stdout);
+ fputsln(_(" -v, --verbose verbose"), stdout);
+ fprintf(stdout, USAGE_HELP_OPTIONS(20));
+ fprintf(stdout, USAGE_MAN_TAIL("coresched(1)"));
+ exit(EXIT_SUCCESS);
+}
+
+#define bad_usage(FMT...) \
+ do { \
+ warnx(FMT); \
+ errtryhelp(EXIT_FAILURE); \
+ } while (0)
+
+static sched_core_cookie core_sched_get_cookie(pid_t pid)
+{
+ sched_core_cookie cookie = 0;
+ if (prctl(PR_SCHED_CORE, PR_SCHED_CORE_GET, pid,
+ PR_SCHED_CORE_SCOPE_THREAD, &cookie))
+ err(EXIT_FAILURE, _("Failed to get cookie from PID %d"), pid);
+ return cookie;
+}
+
+static void core_sched_create_cookie(pid_t pid, sched_core_scope type)
+{
+ if (prctl(PR_SCHED_CORE, PR_SCHED_CORE_CREATE, pid, type, 0))
+ err(EXIT_FAILURE, _("Failed to create cookie for PID %d"), pid);
+}
+
+static void core_sched_pull_cookie(pid_t from)
+{
+ if (prctl(PR_SCHED_CORE, PR_SCHED_CORE_SHARE_FROM, from,
+ PR_SCHED_CORE_SCOPE_THREAD, 0))
+ err(EXIT_FAILURE, _("Failed to pull cookie from PID %d"), from);
+}
+
+static void core_sched_push_cookie(pid_t to, sched_core_scope type)
+{
+ if (prctl(PR_SCHED_CORE, PR_SCHED_CORE_SHARE_TO, to, type, 0))
+ err(EXIT_FAILURE, _("Failed to push cookie to PID %d"), to);
+}
+
+static void core_sched_copy_cookie(pid_t from, pid_t to,
+ sched_core_scope to_type)
+{
+ core_sched_pull_cookie(from);
+ core_sched_push_cookie(to, to_type);
+
+ if (sched_core_verbose) {
+ sched_core_cookie before = core_sched_get_cookie(from);
+ warnx(_("copied cookie 0x%llx from PID %d to PID %d"), before,
+ from, to);
+ }
+}
+
+static void core_sched_get_and_print_cookie(pid_t pid)
+{
+ if (sched_core_verbose) {
+ sched_core_cookie after = core_sched_get_cookie(pid);
+ warnx(_("set cookie of PID %d to 0x%llx"), pid, after);
+ }
+}
+
+static void core_sched_exec_with_cookie(struct args *args, char **argv)
+{
+ // Move the argument list to the first argument of the program
+ argv = &argv[args->exec_argv_offset];
+
+ // If a source PID is provided, try to copy the cookie from
+ // that PID. Otherwise, create a brand new cookie with the
+ // provided type.
+ if (args->src) {
+ core_sched_pull_cookie(args->src);
+ core_sched_get_and_print_cookie(args->src);
+ } else {
+ pid_t pid = getpid();
+ core_sched_create_cookie(pid, args->type);
+ core_sched_get_and_print_cookie(pid);
+ }
+
+ if (execvp(argv[0], argv))
+ errexec(argv[0]);
+}
+
+// There are two failure conditions for the core scheduling prctl calls
+// that rely on the environment in which coresched is running.
+// 1. If PR_SCHED_CORE is not recognized, or not supported on this system,
+// then prctl will set errno to EINVAL. Assuming all other operands of
+// prctl are valid, we can use errno==EINVAL as a check to see whether
+// core scheduling is available on this system.
+// 2. prctl sets errno to ENODEV if SMT is not available on this system,
+// either because SMT support has been disabled in the kernel, or because
+// the hardware doesn't support it.
+static bool is_core_sched_supported(void)
+{
+ sched_core_cookie cookie = 0;
+ if (prctl(PR_SCHED_CORE, PR_SCHED_CORE_GET, getpid(),
+ PR_SCHED_CORE_SCOPE_THREAD, &cookie))
+ if (errno == EINVAL || errno == ENODEV)
+ return false;
+
+ return true;
+}
+
+static sched_core_scope parse_core_sched_type(char *str)
+{
+ if (!strcmp(str, "pid"))
+ return PR_SCHED_CORE_SCOPE_THREAD;
+ else if (!strcmp(str, "tgid"))
+ return PR_SCHED_CORE_SCOPE_THREAD_GROUP;
+ else if (!strcmp(str, "pgid"))
+ return PR_SCHED_CORE_SCOPE_PROCESS_GROUP;
+
+ bad_usage(_("'%s' is an invalid option. Must be one of pid/tgid/pgid"),
+ str);
+}
+
+static void parse_and_verify_arguments(int argc, char **argv, struct args *args)
+{
+ int c;
+
+ static const struct option longopts[] = {
+ { "source", required_argument, NULL, 's' },
+ { "dest", required_argument, NULL, 'd' },
+ { "dest-type", required_argument, NULL, 't' },
+ { "verbose", no_argument, NULL, 'v' },
+ { "version", no_argument, NULL, 'V' },
+ { "help", no_argument, NULL, 'h' },
+ { NULL, 0, NULL, 0 }
+ };
+
+ while ((c = getopt_long(argc, argv, "s:d:t:vVh", longopts, NULL)) != -1)
+ switch (c) {
+ case 's':
+ args->src = strtopid_or_err(
+ optarg,
+ _("Failed to parse PID for -s/--source"));
+ break;
+ case 'd':
+ args->dest = strtopid_or_err(
+ optarg, _("Failed to parse PID for -d/--dest"));
+ break;
+ case 't':
+ args->type = parse_core_sched_type(optarg);
+ break;
+ case 'v':
+ sched_core_verbose = true;
+ break;
+ case 'V':
+ print_version(EXIT_SUCCESS);
+ case 'h':
+ usage();
+ default:
+ errtryhelp(EXIT_FAILURE);
+ }
+
+ if (argc <= optind) {
+ args->cmd = SCHED_CORE_CMD_GET;
+ } else {
+ if (!strcmp(argv[optind], "get"))
+ args->cmd = SCHED_CORE_CMD_GET;
+ else if (!strcmp(argv[optind], "new"))
+ args->cmd = SCHED_CORE_CMD_NEW;
+ else if (!strcmp(argv[optind], "copy"))
+ args->cmd = SCHED_CORE_CMD_COPY;
+ else
+ bad_usage(_("Unknown function"));
+
+ // Since we parsed an extra "option" outside of getopt_long, we have to
+ // increment optind manually.
+ ++optind;
+ }
+
+ if (args->cmd == SCHED_CORE_CMD_GET && args->dest)
+ bad_usage(_("get does not accept the --dest option"));
+
+ if (args->cmd == SCHED_CORE_CMD_NEW && args->src)
+ bad_usage(_("new does not accept the --source option"));
+
+ // If the -s/--source option is not specified, it defaults to the PID
+ // of the current coresched process
+ if (args->cmd != SCHED_CORE_CMD_NEW && !args->src)
+ args->src = getpid();
+
+ // More arguments have been passed, which means that the user wants to run
+ // another program with a core scheduling cookie.
+ if (argc > optind) {
+ switch (args->cmd) {
+ case SCHED_CORE_CMD_GET:
+ bad_usage(_("bad usage of the get function"));
+ break;
+ case SCHED_CORE_CMD_NEW:
+ if (args->dest)
+ bad_usage(_(
+ "new requires either a -d/--dest or a command"));
+ else
+ args->exec_argv_offset = optind;
+ break;
+ case SCHED_CORE_CMD_COPY:
+ if (args->dest)
+ bad_usage(_(
+ "copy requires either a -d/--dest or a command"));
+ else
+ args->exec_argv_offset = optind;
+ break;
+ }
+ } else {
+ if (args->cmd == SCHED_CORE_CMD_NEW && !args->dest)
+ bad_usage(_(
+ "new requires either a -d/--dest or a command"));
+ if (args->cmd == SCHED_CORE_CMD_COPY && !args->dest)
+ bad_usage(_(
+ "copy requires either a -d/--dest or a command"));
+ }
+}
+
+int main(int argc, char **argv)
+{
+ struct args args = { .type = PR_SCHED_CORE_SCOPE_THREAD_GROUP };
+
+ setlocale(LC_ALL, "");
+ bindtextdomain(PACKAGE, LOCALEDIR);
+ textdomain(PACKAGE);
+ close_stdout_atexit();
+
+ parse_and_verify_arguments(argc, argv, &args);
+
+ if (!is_core_sched_supported())
+ errx(EXIT_FAILURE,
+ _("Core scheduling is not supported on this system. Either SMT "
+ "is unavailable or your kernel does not support CONFIG_SCHED_CORE."));
+
+ sched_core_cookie cookie;
+
+ switch (args.cmd) {
+ case SCHED_CORE_CMD_GET:
+ cookie = core_sched_get_cookie(args.src);
+ printf(_("cookie of pid %d is 0x%llx\n"), args.src, cookie);
+ break;
+ case SCHED_CORE_CMD_NEW:
+ if (args.exec_argv_offset) {
+ core_sched_exec_with_cookie(&args, argv);
+ } else {
+ core_sched_create_cookie(args.dest, args.type);
+ core_sched_get_and_print_cookie(args.dest);
+ }
+ break;
+ case SCHED_CORE_CMD_COPY:
+ if (args.exec_argv_offset)
+ core_sched_exec_with_cookie(&args, argv);
+ else
+ core_sched_copy_cookie(args.src, args.dest, args.type);
+ break;
+ default:
+ usage();
+ }
+}
--- /dev/null
+#!/bin/bash
+# SPDX-License-Identifier: EUPL-1.2
+#
+# This file is part of util-linux
+#
+# Copyright (C) 2024 Thijs Raymakers
+# Licensed under the EUPL v1.2
+
+TS_TOPDIR="${0%/*}/../.."
+TS_DESC="coresched"
+
+. "$TS_TOPDIR"/functions.sh
+ts_init "$*"
+
+ts_check_test_command "$TS_CMD_CORESCHED"
+ts_check_prog "tee"
+ts_check_prog "sed"
+
+# If coresched cannot succesfully run, skip the test suite
+CORESCHED_TEST_KERNEL_SUPPORT_CMD=$($TS_CMD_CORESCHED 2>&1)
+if [[ $CORESCHED_TEST_KERNEL_SUPPORT_CMD == *"CONFIG_SCHED_CORE"* ]]; then
+ ts_skip "Kernel has no CONFIG_SCHED_CORE support or SMT is not available"
+fi
+
+# The output of coresched contains PIDs and core scheduling cookies, both of which should be
+# assumed to be random values as we have no control over them. The tests replace these values
+# with sed before writing them to the output file, so it can match the expected output file.
+# - The PID of this bash script is replaced with the placeholder `OWN_PID`
+# - The core scheduling cookie of this bash script is replaced by `COOKIE`
+# - Any other cookie is replaced by `DIFFERENT_COOKIE`
+# The behavior of coresched does not depend on the exact values of these cookies, so using
+# placeholder values does not change the behavior tests.
+ts_init_subtest "set-cookie-parent-pid"
+CORESCHED_OUTPUT=$( ($TS_CMD_CORESCHED -v new -d $$ \
+ | tee -a "$TS_OUTPUT") 3>&1 1>&2 2>&3 \
+ | sed "s/$$/PARENT_PID/g")
+CORESCHED_PARENT_COOKIE=$(echo "$CORESCHED_OUTPUT" | sed 's/^.*\(0x.*$\)/\1/g')
+if [ -z "$CORESCHED_PARENT_COOKIE" ]; then
+ ts_failed "empty value for CORESCHED_PARENT_COOKIE"
+fi
+CORESCHED_OUTPUT=$(echo "$CORESCHED_OUTPUT" \
+ | sed "s/$CORESCHED_PARENT_COOKIE/PARENT_COOKIE/g")
+echo "$CORESCHED_OUTPUT" >> "$TS_ERRLOG"
+ts_finalize_subtest
+
+ts_init_subtest "get-cookie-parent-pid"
+$TS_CMD_CORESCHED get -s $$ 2>> "$TS_ERRLOG" \
+ | sed -e "s/$$/PARENT_PID/g" \
+ -e "s/$CORESCHED_PARENT_COOKIE/PARENT_COOKIE/g" >> "$TS_OUTPUT"
+ts_finalize_subtest
+
+ts_init_subtest "get-cookie-own-pid"
+$TS_CMD_CORESCHED get 2>> "$TS_ERRLOG" \
+ | sed -e "s/pid [0-9]\+/pid OWN_PID/g" \
+ -e "s/$CORESCHED_PARENT_COOKIE/PARENT_COOKIE/g" >> "$TS_OUTPUT"
+ts_finalize_subtest
+
+ts_init_subtest "new-child-with-new-cookie"
+$TS_CMD_CORESCHED new -- "$TS_CMD_CORESCHED" get 2>> "$TS_ERRLOG" \
+ | sed -e 's/^.*\(0x.*$\)/\1/g' \
+ -e "s/$CORESCHED_PARENT_COOKIE/SAME_COOKIE/g" \
+ -e "s/0x.*$/DIFFERENT_COOKIE/g" >> "$TS_OUTPUT"
+ts_finalize_subtest
+
+ts_init_subtest "copy-from-parent-to-nested-child"
+$TS_CMD_CORESCHED new -- /bin/bash -c \
+ "$TS_CMD_CORESCHED copy -s $$ -- $TS_CMD_CORESCHED get" \
+2>> "$TS_ERRLOG" \
+ | sed -e 's/^.*\(0x.*$\)/\1/g' \
+ -e "s/$CORESCHED_PARENT_COOKIE/SAME_COOKIE/g" \
+ -e "s/0x.*$/DIFFERENT_COOKIE/g" >> "$TS_OUTPUT"
+ts_finalize_subtest
+
+ts_init_subtest "copy-from-child-to-parent"
+$TS_CMD_CORESCHED new -- /bin/bash -c \
+ "$TS_CMD_CORESCHED copy -s \$\$ -d $$"
+$TS_CMD_CORESCHED get 2>> "$TS_ERRLOG" \
+ | sed -e 's/^.*\(0x.*$\)/\1/g' \
+ -e "s/$CORESCHED_PARENT_COOKIE/SAME_COOKIE/g" \
+ -e "s/0x.*$/DIFFERENT_COOKIE/g" >> "$TS_OUTPUT"
+ts_finalize_subtest
+
+ts_finalize
projects / thirdparty / util-linux.git / commitdiff
