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Based on 1 normalized pattern(s): 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 extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 114 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Allison Randal <allison@lohutok.net> Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190520170857.552531963@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
55 lines
1.2 KiB
C
55 lines
1.2 KiB
C
// 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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