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/* 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>

/*

* Returns true if the task does not share ->mm with another thread/process.

*/

bool current_is_single_threaded(void)

{

struct task_struct *task = current;

struct mm_struct *mm = task->mm;

struct task_struct *p, *t;

bool ret;

if (atomic_read(&task->signal->live) != 1)

return false;

if (atomic_read(&mm->mm_users) == 1)

return true;

ret = false;

rcu_read_lock();

for_each_process(p) {

if (unlikely(p->flags & PF_KTHREAD))

continue;

if (unlikely(p == task->group_leader))

continue;

t = p;

do {

if (unlikely(t->mm == mm))

goto found;

if (likely(t->mm))

break;

/*

* t->mm == NULL. Make sure next_thread/next_task

* will see other CLONE_VM tasks which might be

* forked before exiting.

*/

smp_rmb();

} while_each_thread(p, t);

}

ret = true;

found:

rcu_read_unlock();

return ret;

}