1 // SPDX-License-Identifier: GPL-2.0-or-later << 2 /* Function to determine if a thread group is 1 /* Function to determine if a thread group is single threaded or not 3 * 2 * 4 * Copyright (C) 2008 Red Hat, Inc. All Rights 3 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved. 5 * Written by David Howells (dhowells@redhat.c 4 * Written by David Howells (dhowells@redhat.com) 6 * - Derived from security/selinux/hooks.c 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. 7 */ 11 */ 8 #include <linux/sched/signal.h> !! 12 9 #include <linux/sched/task.h> !! 13 #include <linux/sched.h> 10 #include <linux/sched/mm.h> << 11 14 12 /* 15 /* 13 * Returns true if the task does not share ->m 16 * Returns true if the task does not share ->mm with another thread/process. 14 */ 17 */ 15 bool current_is_single_threaded(void) 18 bool current_is_single_threaded(void) 16 { 19 { 17 struct task_struct *task = current; 20 struct task_struct *task = current; 18 struct mm_struct *mm = task->mm; 21 struct mm_struct *mm = task->mm; 19 struct task_struct *p, *t; 22 struct task_struct *p, *t; 20 bool ret; 23 bool ret; 21 24 22 if (atomic_read(&task->signal->live) ! 25 if (atomic_read(&task->signal->live) != 1) 23 return false; 26 return false; 24 27 25 if (atomic_read(&mm->mm_users) == 1) 28 if (atomic_read(&mm->mm_users) == 1) 26 return true; 29 return true; 27 30 28 ret = false; 31 ret = false; 29 rcu_read_lock(); 32 rcu_read_lock(); 30 for_each_process(p) { 33 for_each_process(p) { 31 if (unlikely(p->flags & PF_KTH 34 if (unlikely(p->flags & PF_KTHREAD)) 32 continue; 35 continue; 33 if (unlikely(p == task->group_ 36 if (unlikely(p == task->group_leader)) 34 continue; 37 continue; 35 38 36 for_each_thread(p, t) { 39 for_each_thread(p, t) { 37 if (unlikely(t->mm == 40 if (unlikely(t->mm == mm)) 38 goto found; 41 goto found; 39 if (likely(t->mm)) 42 if (likely(t->mm)) 40 break; 43 break; 41 /* 44 /* 42 * t->mm == NULL. Make 45 * t->mm == NULL. Make sure next_thread/next_task 43 * will see other CLON 46 * will see other CLONE_VM tasks which might be 44 * forked before exiti 47 * forked before exiting. 45 */ 48 */ 46 smp_rmb(); 49 smp_rmb(); 47 } 50 } 48 } 51 } 49 ret = true; 52 ret = true; 50 found: 53 found: 51 rcu_read_unlock(); 54 rcu_read_unlock(); 52 55 53 return ret; 56 return ret; 54 } 57 } 55 58
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