proc: change first_tid() to use while_each_thread() rather than next_thread()

Rerwrite the main loop to use while_each_thread() instead of
next_thread().  We are going to fix or replace while_each_thread(),
next_thread() should be avoided whenever possible.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Sameer Nanda <snanda@chromium.org>
Cc: Sergey Dyasly <dserrg@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/base.c b/fs/proc/base.c
index f223a56..be8e17c 100644 (file)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -3106,23 +3106,23 @@ static struct task_struct *first_tid(struct task_struct *leader,
        }
 
        /* If nr exceeds the number of threads there is nothing todo */
-       pos = NULL;
        if (nr && nr >= get_nr_threads(leader))
-               goto out;
+               goto fail;
        /* It could be unhashed before we take rcu lock */
        if (!pid_alive(leader))
-               goto out;
+               goto fail;
 
        /* If we haven't found our starting place yet start
         * with the leader and walk nr threads forward.
         */
-       for (pos = leader; nr > 0; --nr) {
-               pos = next_thread(pos);
-               if (pos == leader) {
-                       pos = NULL;
-                       goto out;
-               }
-       }
+       pos = leader;
+       do {
+               if (nr-- <= 0)
+                       goto found;
+       } while_each_thread(leader, pos);
+fail:
+       pos = NULL;
+       goto out;
 found:
        get_task_struct(pos);
 out: