is_single_threaded.c
1.17 KB
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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>
/**
* 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;
}