Branch data Line data Source code
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 : 0 : bool current_is_single_threaded(void)
19 : : {
20 : 0 : struct task_struct *task = current;
21 : 0 : struct mm_struct *mm = task->mm;
22 : : struct task_struct *p, *t;
23 : : bool ret;
24 : :
25 [ # # ]: 0 : if (atomic_read(&task->signal->live) != 1)
26 : : return false;
27 : :
28 [ # # ]: 0 : if (atomic_read(&mm->mm_users) == 1)
29 : : return true;
30 : :
31 : : ret = false;
32 : : rcu_read_lock();
33 [ # # ]: 0 : for_each_process(p) {
34 [ # # ]: 0 : if (unlikely(p->flags & PF_KTHREAD))
35 : 0 : continue;
36 [ # # ]: 0 : if (unlikely(p == task->group_leader))
37 : 0 : continue;
38 : :
39 : : t = p;
40 : : do {
41 [ # # ]: 0 : if (unlikely(t->mm == mm))
42 : : goto found;
43 [ # # ]: 0 : 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 : 0 : smp_rmb();
51 [ # # ]: 0 : } while_each_thread(p, t);
52 : : }
53 : : ret = true;
54 : : found:
55 : : rcu_read_unlock();
56 : :
57 : 0 : return ret;
58 : : }
|