1*6cc88bc4SDavid Howells /* Function to determine if a thread group is single threaded or not 2*6cc88bc4SDavid Howells * 3*6cc88bc4SDavid Howells * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved. 4*6cc88bc4SDavid Howells * Written by David Howells (dhowells@redhat.com) 5*6cc88bc4SDavid Howells * - Derived from security/selinux/hooks.c 6*6cc88bc4SDavid Howells * 7*6cc88bc4SDavid Howells * This program is free software; you can redistribute it and/or 8*6cc88bc4SDavid Howells * modify it under the terms of the GNU General Public Licence 9*6cc88bc4SDavid Howells * as published by the Free Software Foundation; either version 10*6cc88bc4SDavid Howells * 2 of the Licence, or (at your option) any later version. 11*6cc88bc4SDavid Howells */ 12*6cc88bc4SDavid Howells 13*6cc88bc4SDavid Howells #include <linux/sched.h> 14*6cc88bc4SDavid Howells 15*6cc88bc4SDavid Howells /** 16*6cc88bc4SDavid Howells * is_single_threaded - Determine if a thread group is single-threaded or not 17*6cc88bc4SDavid Howells * @p: A task in the thread group in question 18*6cc88bc4SDavid Howells * 19*6cc88bc4SDavid Howells * This returns true if the thread group to which a task belongs is single 20*6cc88bc4SDavid Howells * threaded, false if it is not. 21*6cc88bc4SDavid Howells */ 22*6cc88bc4SDavid Howells bool is_single_threaded(struct task_struct *p) 23*6cc88bc4SDavid Howells { 24*6cc88bc4SDavid Howells struct task_struct *g, *t; 25*6cc88bc4SDavid Howells struct mm_struct *mm = p->mm; 26*6cc88bc4SDavid Howells 27*6cc88bc4SDavid Howells if (atomic_read(&p->signal->count) != 1) 28*6cc88bc4SDavid Howells goto no; 29*6cc88bc4SDavid Howells 30*6cc88bc4SDavid Howells if (atomic_read(&p->mm->mm_users) != 1) { 31*6cc88bc4SDavid Howells read_lock(&tasklist_lock); 32*6cc88bc4SDavid Howells do_each_thread(g, t) { 33*6cc88bc4SDavid Howells if (t->mm == mm && t != p) 34*6cc88bc4SDavid Howells goto no_unlock; 35*6cc88bc4SDavid Howells } while_each_thread(g, t); 36*6cc88bc4SDavid Howells read_unlock(&tasklist_lock); 37*6cc88bc4SDavid Howells } 38*6cc88bc4SDavid Howells 39*6cc88bc4SDavid Howells return true; 40*6cc88bc4SDavid Howells 41*6cc88bc4SDavid Howells no_unlock: 42*6cc88bc4SDavid Howells read_unlock(&tasklist_lock); 43*6cc88bc4SDavid Howells no: 44*6cc88bc4SDavid Howells return false; 45*6cc88bc4SDavid Howells } 46