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
9 #include <linux/sched/task.h> !! 13 #include <linux/sched.h>
10 #include <linux/sched/mm.h> <<
11 14
12 /* 15 /*
13 * Returns true if the task does not share ->m 16 * Returns true if the task does not share ->mm with another thread/process.
14 */ 17 */
15 bool current_is_single_threaded(void) 18 bool current_is_single_threaded(void)
16 { 19 {
17 struct task_struct *task = current; 20 struct task_struct *task = current;
18 struct mm_struct *mm = task->mm; 21 struct mm_struct *mm = task->mm;
19 struct task_struct *p, *t; 22 struct task_struct *p, *t;
20 bool ret; 23 bool ret;
21 24
22 if (atomic_read(&task->signal->live) ! 25 if (atomic_read(&task->signal->live) != 1)
23 return false; 26 return false;
24 27
25 if (atomic_read(&mm->mm_users) == 1) 28 if (atomic_read(&mm->mm_users) == 1)
26 return true; 29 return true;
27 30
28 ret = false; 31 ret = false;
29 rcu_read_lock(); 32 rcu_read_lock();
30 for_each_process(p) { 33 for_each_process(p) {
31 if (unlikely(p->flags & PF_KTH 34 if (unlikely(p->flags & PF_KTHREAD))
32 continue; 35 continue;
33 if (unlikely(p == task->group_ 36 if (unlikely(p == task->group_leader))
34 continue; 37 continue;
35 38
36 for_each_thread(p, t) { 39 for_each_thread(p, t) {
37 if (unlikely(t->mm == 40 if (unlikely(t->mm == mm))
38 goto found; 41 goto found;
39 if (likely(t->mm)) 42 if (likely(t->mm))
40 break; 43 break;
41 /* 44 /*
42 * t->mm == NULL. Make 45 * t->mm == NULL. Make sure next_thread/next_task
43 * will see other CLON 46 * will see other CLONE_VM tasks which might be
44 * forked before exiti 47 * forked before exiting.
45 */ 48 */
46 smp_rmb(); 49 smp_rmb();
47 } 50 }
48 } 51 }
49 ret = true; 52 ret = true;
50 found: 53 found:
51 rcu_read_unlock(); 54 rcu_read_unlock();
52 55
53 return ret; 56 return ret;
54 } 57 }
55 58
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