/* Function to determine if a thread group is single threaded or not * * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) * - Derived from security/selinux/hooks.c * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public Licence * as published by the Free Software Foundation; either version * 2 of the Licence, or (at your option) any later version. */ #include <linux/sched.h> /** * is_single_threaded - Determine if a thread group is single-threaded or not * @p: A task in the thread group in question * * This returns true if the thread group to which a task belongs is single * threaded, false if it is not. */ bool is_single_threaded(struct task_struct *p) { struct task_struct *g, *t; struct mm_struct *mm = p->mm; if (atomic_read(&p->signal->count) != 1) goto no; if (atomic_read(&p->mm->mm_users) != 1) { read_lock(&tasklist_lock); do_each_thread(g, t) { if (t->mm == mm && t != p) goto no_unlock; } while_each_thread(g, t); read_unlock(&tasklist_lock); } return true; no_unlock: read_unlock(&tasklist_lock); no: return false; }