is_single_threaded.c

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    1 /* Function to determine if a thread group is single threaded or not
    2  *
    3  * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
    4  * Written by David Howells (dhowells@redhat.com)
    5  * - Derived from security/selinux/hooks.c
    6  *
    7  * This program is free software; you can redistribute it and/or
    8  * modify it under the terms of the GNU General Public Licence
    9  * as published by the Free Software Foundation; either version
   10  * 2 of the Licence, or (at your option) any later version.
   11  */
   12 
   13 #include <linux/sched.h>
   14 
   15 /*
   16  * Returns true if the task does not share ->mm with another thread/process.
   17  */
   18 bool current_is_single_threaded(void)
   19 {
   20         struct task_struct *task = current;
   21         struct mm_struct *mm = task->mm;
   22         struct task_struct *p, *t;
   23         bool ret;
   24 
   25         if (atomic_read(&task->signal->live) != 1)
   26                 return false;
   27 
   28         if (atomic_read(&mm->mm_users) == 1)
   29                 return true;
   30 
   31         ret = false;
   32         rcu_read_lock();
   33         for_each_process(p) {
   34                 if (unlikely(p->flags & PF_KTHREAD))
   35                         continue;
   36                 if (unlikely(p == task->group_leader))
   37                         continue;
   38 
   39                 t = p;
   40                 do {
   41                         if (unlikely(t->mm == mm))
   42                                 goto found;
   43                         if (likely(t->mm))
   44                                 break;
   45                         /*
   46                          * t->mm == NULL. Make sure next_thread/next_task
   47                          * will see other CLONE_VM tasks which might be
   48                          * forked before exiting.
   49                          */
   50                         smp_rmb();
   51                 } while_each_thread(p, t);
   52         }
   53         ret = true;
   54 found:
   55         rcu_read_unlock();
   56 
   57         return ret;
   58 }

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FreeBSD/Linux Kernel Cross Reference sys/lib/is_single_threaded.c

FreeBSD/Linux Kernel Cross Reference
sys/lib/is_single_threaded.c