exit: reparent: introduce find_alive_thread()

Add the new simple helper to factor out the for_each_thread() code in
find_child_reaper() and find_new_reaper().  It can also simplify the
potential PF_EXITING -> exit_state change, plus perhaps we can change this
code to take SIGNAL_GROUP_EXIT into account.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Aaron Tomlin <atomlin@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Kay Sievers <kay@vrfy.org>
Cc: Lennart Poettering <lennart@poettering.net>
Cc: Sterling Alexander <stalexan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/exit.c b/kernel/exit.c
index 930fbe1..b0f482f 100644 (file)
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -459,6 +459,17 @@ static void exit_mm(struct task_struct *tsk)
        clear_thread_flag(TIF_MEMDIE);
 }
 
+static struct task_struct *find_alive_thread(struct task_struct *p)
+{
+       struct task_struct *t;
+
+       for_each_thread(p, t) {
+               if (!(t->flags & PF_EXITING))
+                       return t;
+       }
+       return NULL;
+}
+
 static struct task_struct *find_child_reaper(struct task_struct *father)
        __releases(&tasklist_lock)
        __acquires(&tasklist_lock)
@@ -469,9 +480,8 @@ static struct task_struct *find_child_reaper(struct task_struct *father)
        if (likely(reaper != father))
                return reaper;
 
-       for_each_thread(father, reaper) {
-               if (reaper->flags & PF_EXITING)
-                       continue;
+       reaper = find_alive_thread(father);
+       if (reaper) {
                pid_ns->child_reaper = reaper;
                return reaper;
        }
@@ -497,16 +507,13 @@ static struct task_struct *find_child_reaper(struct task_struct *father)
 static struct task_struct *find_new_reaper(struct task_struct *father,
                                           struct task_struct *child_reaper)
 {
-       struct task_struct *thread;
+       struct task_struct *thread, *reaper;
 
-       for_each_thread(father, thread) {
-               if (thread->flags & PF_EXITING)
-                       continue;
+       thread = find_alive_thread(father);
+       if (thread)
                return thread;
-       }
 
        if (father->signal->has_child_subreaper) {
-               struct task_struct *reaper;
                /*
                 * Find the first ->is_child_subreaper ancestor in our pid_ns.
                 * We start from father to ensure we can not look into another
@@ -520,10 +527,9 @@ static struct task_struct *find_new_reaper(struct task_struct *father,
                                break;
                        if (!reaper->signal->is_child_subreaper)
                                continue;
-                       for_each_thread(reaper, thread) {
-                               if (!(thread->flags & PF_EXITING))
-                                       return thread;
-                       }
+                       thread = find_alive_thread(reaper);
+                       if (thread)
+                               return thread;
                }
        }