diff options
Diffstat (limited to 'lib/is_single_threaded.c')
-rw-r--r-- | lib/is_single_threaded.c | 58 |
1 files changed, 58 insertions, 0 deletions
diff --git a/lib/is_single_threaded.c b/lib/is_single_threaded.c new file mode 100644 index 00000000..bd2bea96 --- /dev/null +++ b/lib/is_single_threaded.c @@ -0,0 +1,58 @@ +/* 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 (dhowells@redhat.com) + * - 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.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; + + t = p; + do { + 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(); + } while_each_thread(p, t); + } + ret = true; +found: + rcu_read_unlock(); + + return ret; +} |