oss: Mark loadhex static in hex2hex.c
[linux-2.6.git] / lib / is_single_threaded.c
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                 t = p;
40                 do {
41                         if (unlikely(t->mm == mm))
42                                 goto found;
43                         if (likely(t->mm))
44                                 break;
45                         /*
46                          * t->mm == NULL. Make sure next_thread/next_task
47                          * will see other CLONE_VM tasks which might be
48                          * forked before exiting.
49                          */
50                         smp_rmb();
51                 } while_each_thread(p, t);
52         }
53         ret = true;
54 found:
55         rcu_read_unlock();
56
57         return ret;
58 }