blob: 391fd23976a2c00fc9c08cfe6e2a2ab44953c5cf
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 | */ |
18 | bool 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 | for_each_thread(p, t) { |
40 | if (unlikely(t->mm == mm)) |
41 | goto found; |
42 | if (likely(t->mm)) |
43 | break; |
44 | /* |
45 | * t->mm == NULL. Make sure next_thread/next_task |
46 | * will see other CLONE_VM tasks which might be |
47 | * forked before exiting. |
48 | */ |
49 | smp_rmb(); |
50 | } |
51 | } |
52 | ret = true; |
53 | found: |
54 | rcu_read_unlock(); |
55 | |
56 | return ret; |
57 | } |
58 |