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>

1 files changed, 19 insertions, 13 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index 930fbe1b5ee2..b0f482f5daf9 100644
--- 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;
                 }
         }