cregit-Linux how code gets into the kernel

Release 4.16 lib/is_single_threaded.c

Directory: lib
/* 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 (
 * - Derived from security/selinux/hooks.c
 * 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.
#include <linux/sched/signal.h>
#include <linux/sched/task.h>
#include <linux/sched/mm.h>

 * Returns true if the task does not share ->mm with another thread/process.

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


Oleg Nesterov9462.25%480.00%
David Howells5737.75%120.00%

Overall Contributors

Oleg Nesterov9558.64%450.00%
David Howells6037.04%112.50%
Ingo Molnar74.32%337.50%
Directory: lib
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