1 // SPDX-License-Identifier: GPL-2.0-or-later <<
2 /* Function to determine if a thread group is 1 /* Function to determine if a thread group is single threaded or not
3 * 2 *
4 * Copyright (C) 2008 Red Hat, Inc. All Rights 3 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.c 4 * Written by David Howells (dhowells@redhat.com)
6 * - Derived from security/selinux/hooks.c 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.
7 */ 11 */
8 #include <linux/sched/signal.h> 12 #include <linux/sched/signal.h>
9 #include <linux/sched/task.h> 13 #include <linux/sched/task.h>
10 #include <linux/sched/mm.h> 14 #include <linux/sched/mm.h>
11 15
12 /* 16 /*
13 * Returns true if the task does not share ->m 17 * Returns true if the task does not share ->mm with another thread/process.
14 */ 18 */
15 bool current_is_single_threaded(void) 19 bool current_is_single_threaded(void)
16 { 20 {
17 struct task_struct *task = current; 21 struct task_struct *task = current;
18 struct mm_struct *mm = task->mm; 22 struct mm_struct *mm = task->mm;
19 struct task_struct *p, *t; 23 struct task_struct *p, *t;
20 bool ret; 24 bool ret;
21 25
22 if (atomic_read(&task->signal->live) ! 26 if (atomic_read(&task->signal->live) != 1)
23 return false; 27 return false;
24 28
25 if (atomic_read(&mm->mm_users) == 1) 29 if (atomic_read(&mm->mm_users) == 1)
26 return true; 30 return true;
27 31
28 ret = false; 32 ret = false;
29 rcu_read_lock(); 33 rcu_read_lock();
30 for_each_process(p) { 34 for_each_process(p) {
31 if (unlikely(p->flags & PF_KTH 35 if (unlikely(p->flags & PF_KTHREAD))
32 continue; 36 continue;
33 if (unlikely(p == task->group_ 37 if (unlikely(p == task->group_leader))
34 continue; 38 continue;
35 39
36 for_each_thread(p, t) { 40 for_each_thread(p, t) {
37 if (unlikely(t->mm == 41 if (unlikely(t->mm == mm))
38 goto found; 42 goto found;
39 if (likely(t->mm)) 43 if (likely(t->mm))
40 break; 44 break;
41 /* 45 /*
42 * t->mm == NULL. Make 46 * t->mm == NULL. Make sure next_thread/next_task
43 * will see other CLON 47 * will see other CLONE_VM tasks which might be
44 * forked before exiti 48 * forked before exiting.
45 */ 49 */
46 smp_rmb(); 50 smp_rmb();
47 } 51 }
48 } 52 }
49 ret = true; 53 ret = true;
50 found: 54 found:
51 rcu_read_unlock(); 55 rcu_read_unlock();
52 56
53 return ret; 57 return ret;
54 } 58 }
55 59
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