16cc88bc4SDavid Howells /* Function to determine if a thread group is single threaded or not 26cc88bc4SDavid Howells * 36cc88bc4SDavid Howells * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved. 46cc88bc4SDavid Howells * Written by David Howells (dhowells@redhat.com) 56cc88bc4SDavid Howells * - Derived from security/selinux/hooks.c 66cc88bc4SDavid Howells * 76cc88bc4SDavid Howells * This program is free software; you can redistribute it and/or 86cc88bc4SDavid Howells * modify it under the terms of the GNU General Public Licence 96cc88bc4SDavid Howells * as published by the Free Software Foundation; either version 106cc88bc4SDavid Howells * 2 of the Licence, or (at your option) any later version. 116cc88bc4SDavid Howells */ 126cc88bc4SDavid Howells 136cc88bc4SDavid Howells #include <linux/sched.h> 146cc88bc4SDavid Howells 15d2e3ee9bSOleg Nesterov /* 16d2e3ee9bSOleg Nesterov * Returns true if the task does not share ->mm with another thread/process. 176cc88bc4SDavid Howells */ 185bb459bbSOleg Nesterov bool current_is_single_threaded(void) 196cc88bc4SDavid Howells { 205bb459bbSOleg Nesterov struct task_struct *task = current; 21d2e3ee9bSOleg Nesterov struct mm_struct *mm = task->mm; 22d2e3ee9bSOleg Nesterov struct task_struct *p, *t; 23d2e3ee9bSOleg Nesterov bool ret; 246cc88bc4SDavid Howells 25d2e3ee9bSOleg Nesterov if (atomic_read(&task->signal->live) != 1) 26d2e3ee9bSOleg Nesterov return false; 276cc88bc4SDavid Howells 28d2e3ee9bSOleg Nesterov if (atomic_read(&mm->mm_users) == 1) 296cc88bc4SDavid Howells return true; 306cc88bc4SDavid Howells 31d2e3ee9bSOleg Nesterov ret = false; 32d2e3ee9bSOleg Nesterov rcu_read_lock(); 33d2e3ee9bSOleg Nesterov for_each_process(p) { 34d2e3ee9bSOleg Nesterov if (unlikely(p->flags & PF_KTHREAD)) 35d2e3ee9bSOleg Nesterov continue; 36d2e3ee9bSOleg Nesterov if (unlikely(p == task->group_leader)) 37d2e3ee9bSOleg Nesterov continue; 38d2e3ee9bSOleg Nesterov 39d2e3ee9bSOleg Nesterov t = p; 40d2e3ee9bSOleg Nesterov do { 41d2e3ee9bSOleg Nesterov if (unlikely(t->mm == mm)) 42d2e3ee9bSOleg Nesterov goto found; 43d2e3ee9bSOleg Nesterov if (likely(t->mm)) 44d2e3ee9bSOleg Nesterov break; 45*967cc537SOleg Nesterov /* 46*967cc537SOleg Nesterov * t->mm == NULL. Make sure next_thread/next_task 47*967cc537SOleg Nesterov * will see other CLONE_VM tasks which might be 48*967cc537SOleg Nesterov * forked before exiting. 49*967cc537SOleg Nesterov */ 50*967cc537SOleg Nesterov smp_rmb(); 51d2e3ee9bSOleg Nesterov } while_each_thread(p, t); 52d2e3ee9bSOleg Nesterov } 53d2e3ee9bSOleg Nesterov ret = true; 54d2e3ee9bSOleg Nesterov found: 55d2e3ee9bSOleg Nesterov rcu_read_unlock(); 56d2e3ee9bSOleg Nesterov 57d2e3ee9bSOleg Nesterov return ret; 586cc88bc4SDavid Howells } 59