1// SPDX-License-Identifier: GPL-2.0-or-later
 2/* Function to determine if a thread group is single threaded or not
 3 *
 4 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
 5 * Written by David Howells (dhowells@redhat.com)
 6 * - Derived from security/selinux/hooks.c
 
 
 
 
 
 7 */
 8#include <linux/sched/signal.h>
 9#include <linux/sched/task.h>
10#include <linux/sched/mm.h>
11
12/*
13 * Returns true if the task does not share ->mm with another thread/process.
14 */
15bool current_is_single_threaded(void)
16{
17	struct task_struct *task = current;
18	struct mm_struct *mm = task->mm;
19	struct task_struct *p, *t;
20	bool ret;
21
22	if (atomic_read(&task->signal->live) != 1)
23		return false;
24
25	if (atomic_read(&mm->mm_users) == 1)
26		return true;
27
28	ret = false;
29	rcu_read_lock();
30	for_each_process(p) {
31		if (unlikely(p->flags & PF_KTHREAD))
32			continue;
33		if (unlikely(p == task->group_leader))
34			continue;
35
36		for_each_thread(p, t) {
 
37			if (unlikely(t->mm == mm))
38				goto found;
39			if (likely(t->mm))
40				break;
41			/*
42			 * t->mm == NULL. Make sure next_thread/next_task
43			 * will see other CLONE_VM tasks which might be
44			 * forked before exiting.
45			 */
46			smp_rmb();
47		}
48	}
49	ret = true;
50found:
51	rcu_read_unlock();
52
53	return ret;
54}

 
 1/* Function to determine if a thread group is single threaded or not
 2 *
 3 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
 4 * Written by David Howells (dhowells@redhat.com)
 5 * - Derived from security/selinux/hooks.c
 6 *
 7 * This program is free software; you can redistribute it and/or
 8 * modify it under the terms of the GNU General Public Licence
 9 * as published by the Free Software Foundation; either version
10 * 2 of the Licence, or (at your option) any later version.
11 */
12
13#include <linux/sched.h>
 
14
15/*
16 * Returns true if the task does not share ->mm with another thread/process.
17 */
18bool current_is_single_threaded(void)
19{
20	struct task_struct *task = current;
21	struct mm_struct *mm = task->mm;
22	struct task_struct *p, *t;
23	bool ret;
24
25	if (atomic_read(&task->signal->live) != 1)
26		return false;
27
28	if (atomic_read(&mm->mm_users) == 1)
29		return true;
30
31	ret = false;
32	rcu_read_lock();
33	for_each_process(p) {
34		if (unlikely(p->flags & PF_KTHREAD))
35			continue;
36		if (unlikely(p == task->group_leader))
37			continue;
38
39		t = p;
40		do {
41			if (unlikely(t->mm == mm))
42				goto found;
43			if (likely(t->mm))
44				break;
45			/*
46			 * t->mm == NULL. Make sure next_thread/next_task
47			 * will see other CLONE_VM tasks which might be
48			 * forked before exiting.
49			 */
50			smp_rmb();
51		} while_each_thread(p, t);
52	}
53	ret = true;
54found:
55	rcu_read_unlock();
56
57	return ret;
58}