ALSA: usb-audio: add support for Akai MPD16

[safe/jmp/linux-2.6] / lib / is_single_threaded.c

diff --git a/lib/is_single_threaded.c b/lib/is_single_threaded.c
index f1ed2fe..bd2bea9 100644 (file)
--- 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;
 }