// SPDX-License-Identifier: GPL-2.0-or-later
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/* Function to determine if a thread group is single threaded or not
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*
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* Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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* - Derived from security/selinux/hooks.c
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*/
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#include <linux/sched/signal.h>
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#include <linux/sched/task.h>
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#include <linux/sched/mm.h>
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/*
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* Returns true if the task does not share ->mm with another thread/process.
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*/
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bool current_is_single_threaded(void)
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{
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struct task_struct *task = current;
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struct mm_struct *mm = task->mm;
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struct task_struct *p, *t;
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bool ret;
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if (atomic_read(&task->signal->live) != 1)
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return false;
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if (atomic_read(&mm->mm_users) == 1)
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return true;
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ret = false;
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rcu_read_lock();
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for_each_process(p) {
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if (unlikely(p->flags & PF_KTHREAD))
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continue;
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if (unlikely(p == task->group_leader))
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continue;
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for_each_thread(p, t) {
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if (unlikely(t->mm == mm))
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goto found;
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if (likely(t->mm))
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break;
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/*
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* t->mm == NULL. Make sure next_thread/next_task
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* will see other CLONE_VM tasks which might be
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* forked before exiting.
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*/
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smp_rmb();
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}
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}
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ret = true;
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found:
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rcu_read_unlock();
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return ret;
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}
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