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 ([email protected]) 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 might_sleep(); 26 27 if (atomic_read(&task->signal->live) != 1) 28 return false; 29 30 if (atomic_read(&mm->mm_users) == 1) 31 return true; 32 33 ret = false; 34 down_write(&mm->mmap_sem); 35 rcu_read_lock(); 36 for_each_process(p) { 37 if (unlikely(p->flags & PF_KTHREAD)) 38 continue; 39 if (unlikely(p == task->group_leader)) 40 continue; 41 42 t = p; 43 do { 44 if (unlikely(t->mm == mm)) 45 goto found; 46 if (likely(t->mm)) 47 break; 48 } while_each_thread(p, t); 49 } 50 ret = true; 51 found: 52 rcu_read_unlock(); 53 up_write(&mm->mmap_sem); 54 55 return ret; 56 } 57