Commit | Line | Data |
---|---|---|
6cc88bc4 DH |
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 | * is_single_threaded - Determine if a thread group is single-threaded or not | |
17 | * @p: A task in the thread group in question | |
18 | * | |
19 | * This returns true if the thread group to which a task belongs is single | |
20 | * threaded, false if it is not. | |
21 | */ | |
22 | bool is_single_threaded(struct task_struct *p) | |
23 | { | |
24 | struct task_struct *g, *t; | |
25 | struct mm_struct *mm = p->mm; | |
26 | ||
27 | if (atomic_read(&p->signal->count) != 1) | |
28 | goto no; | |
29 | ||
30 | if (atomic_read(&p->mm->mm_users) != 1) { | |
31 | read_lock(&tasklist_lock); | |
32 | do_each_thread(g, t) { | |
33 | if (t->mm == mm && t != p) | |
34 | goto no_unlock; | |
35 | } while_each_thread(g, t); | |
36 | read_unlock(&tasklist_lock); | |
37 | } | |
38 | ||
39 | return true; | |
40 | ||
41 | no_unlock: | |
42 | read_unlock(&tasklist_lock); | |
43 | no: | |
44 | return false; | |
45 | } |