diff options
Diffstat (limited to 'lib/is_single_threaded.c')
| -rw-r--r-- | lib/is_single_threaded.c | 61 |
1 files changed, 37 insertions, 24 deletions
diff --git a/lib/is_single_threaded.c b/lib/is_single_threaded.c index f1ed2fe76c6..bd2bea96336 100644 --- a/lib/is_single_threaded.c +++ b/lib/is_single_threaded.c @@ -12,34 +12,47 @@ #include <linux/sched.h> -/** - * is_single_threaded - Determine if a thread group is single-threaded or not - * @p: A task in the thread group in question - * - * This returns true if the thread group to which a task belongs is single - * threaded, false if it is not. +/* + * Returns true if the task does not share ->mm with another thread/process. */ -bool is_single_threaded(struct task_struct *p) +bool current_is_single_threaded(void) { - struct task_struct *g, *t; - struct mm_struct *mm = p->mm; + struct task_struct *task = current; + struct mm_struct *mm = task->mm; + struct task_struct *p, *t; + bool ret; - if (atomic_read(&p->signal->count) != 1) - goto no; + if (atomic_read(&task->signal->live) != 1) + return false; - if (atomic_read(&p->mm->mm_users) != 1) { - read_lock(&tasklist_lock); - do_each_thread(g, t) { - if (t->mm == mm && t != p) - goto no_unlock; - } while_each_thread(g, t); - read_unlock(&tasklist_lock); - } + if (atomic_read(&mm->mm_users) == 1) + return true; - 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(); -no_unlock: - read_unlock(&tasklist_lock); -no: - return false; + return ret; } |