5bb459bb45
- is_single_threaded(task) is not safe unless task == current, we can't use task->signal or task->mm. - it doesn't make sense unless task == current, the task can fork right after the check. Rename it to current_is_single_threaded() and kill the argument. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: David Howells <dhowells@redhat.com> Signed-off-by: James Morris <jmorris@namei.org>
57 lines
1.2 KiB
C
57 lines
1.2 KiB
C
/* 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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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public Licence
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* as published by the Free Software Foundation; either version
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* 2 of the Licence, or (at your option) any later version.
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*/
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#include <linux/sched.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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might_sleep();
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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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down_write(&mm->mmap_sem);
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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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t = p;
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do {
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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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} while_each_thread(p, t);
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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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up_write(&mm->mmap_sem);
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return ret;
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}
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