Thomas Gleixner | b4d0d23 | 2019-05-20 19:08:01 +0200 | [diff] [blame] | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
David Howells | 6cc88bc | 2008-11-14 10:39:21 +1100 | [diff] [blame] | 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 |
David Howells | 6cc88bc | 2008-11-14 10:39:21 +1100 | [diff] [blame] | 7 | */ |
Ingo Molnar | 3f07c01 | 2017-02-08 18:51:30 +0100 | [diff] [blame] | 8 | #include <linux/sched/signal.h> |
Ingo Molnar | 9164bb4 | 2017-02-04 01:20:53 +0100 | [diff] [blame] | 9 | #include <linux/sched/task.h> |
Ingo Molnar | 589ee62 | 2017-02-04 00:16:44 +0100 | [diff] [blame] | 10 | #include <linux/sched/mm.h> |
David Howells | 6cc88bc | 2008-11-14 10:39:21 +1100 | [diff] [blame] | 11 | |
Oleg Nesterov | d2e3ee9 | 2009-07-17 09:09:36 +1000 | [diff] [blame] | 12 | /* |
| 13 | * Returns true if the task does not share ->mm with another thread/process. |
David Howells | 6cc88bc | 2008-11-14 10:39:21 +1100 | [diff] [blame] | 14 | */ |
Oleg Nesterov | 5bb459b | 2009-07-10 03:48:23 +0200 | [diff] [blame] | 15 | bool current_is_single_threaded(void) |
David Howells | 6cc88bc | 2008-11-14 10:39:21 +1100 | [diff] [blame] | 16 | { |
Oleg Nesterov | 5bb459b | 2009-07-10 03:48:23 +0200 | [diff] [blame] | 17 | struct task_struct *task = current; |
Oleg Nesterov | d2e3ee9 | 2009-07-17 09:09:36 +1000 | [diff] [blame] | 18 | struct mm_struct *mm = task->mm; |
| 19 | struct task_struct *p, *t; |
| 20 | bool ret; |
David Howells | 6cc88bc | 2008-11-14 10:39:21 +1100 | [diff] [blame] | 21 | |
Oleg Nesterov | d2e3ee9 | 2009-07-17 09:09:36 +1000 | [diff] [blame] | 22 | if (atomic_read(&task->signal->live) != 1) |
| 23 | return false; |
| 24 | |
| 25 | if (atomic_read(&mm->mm_users) == 1) |
| 26 | return true; |
| 27 | |
| 28 | ret = false; |
Oleg Nesterov | d2e3ee9 | 2009-07-17 09:09:36 +1000 | [diff] [blame] | 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 | |
Oleg Nesterov | 9022435 | 2015-11-06 16:31:26 -0800 | [diff] [blame] | 36 | for_each_thread(p, t) { |
Oleg Nesterov | d2e3ee9 | 2009-07-17 09:09:36 +1000 | [diff] [blame] | 37 | if (unlikely(t->mm == mm)) |
| 38 | goto found; |
| 39 | if (likely(t->mm)) |
| 40 | break; |
Oleg Nesterov | 967cc53 | 2009-07-09 23:28:49 +0200 | [diff] [blame] | 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(); |
Oleg Nesterov | 9022435 | 2015-11-06 16:31:26 -0800 | [diff] [blame] | 47 | } |
David Howells | 6cc88bc | 2008-11-14 10:39:21 +1100 | [diff] [blame] | 48 | } |
Oleg Nesterov | d2e3ee9 | 2009-07-17 09:09:36 +1000 | [diff] [blame] | 49 | ret = true; |
| 50 | found: |
| 51 | rcu_read_unlock(); |
David Howells | 6cc88bc | 2008-11-14 10:39:21 +1100 | [diff] [blame] | 52 | |
Oleg Nesterov | d2e3ee9 | 2009-07-17 09:09:36 +1000 | [diff] [blame] | 53 | return ret; |
David Howells | 6cc88bc | 2008-11-14 10:39:21 +1100 | [diff] [blame] | 54 | } |