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lib/is_single_threaded.c
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// SPDX-License-Identifier: GPL-2.0-or-later |
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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 |
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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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/* * 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; struct task_struct *p, *t; bool ret; |
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if (atomic_read(&task->signal->live) != 1) return false; |
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if (atomic_read(&mm->mm_users) == 1) return true; ret = false; |
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rcu_read_lock(); for_each_process(p) { if (unlikely(p->flags & PF_KTHREAD)) continue; if (unlikely(p == task->group_leader)) continue; |
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for_each_thread(p, t) { |
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if (unlikely(t->mm == mm)) goto found; if (likely(t->mm)) break; |
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/* * t->mm == NULL. Make sure next_thread/next_task * will see other CLONE_VM tasks which might be * forked before exiting. */ smp_rmb(); |
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} |
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} ret = true; found: rcu_read_unlock(); |
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return ret; |
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} |