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 | */ |
15 | bool 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(v: &task->signal->live) != 1) |
23 | return false; |
24 | |
25 | if (atomic_read(v: &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; |
50 | found: |
51 | rcu_read_unlock(); |
52 | |
53 | return ret; |
54 | } |
55 |