ptrace: introduce ptrace_reparented() helper

Add another trivial helper for the sake of grep.  It also auto-documents the
fact that ->parent != real_parent implies ->ptrace.

No functional changes.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 8 insertions, 5 deletions

diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index ebe0c17039cf..f98501ba557e 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -98,6 +98,10 @@ extern void ptrace_untrace(struct task_struct *child);
 extern int ptrace_may_attach(struct task_struct *task);
 extern int __ptrace_may_attach(struct task_struct *task);
 
+static inline int ptrace_reparented(struct task_struct *child)
+{
+        return child->real_parent != child->parent;
+}
 static inline void ptrace_link(struct task_struct *child,
                                struct task_struct *new_parent)
 {
diff --git a/kernel/exit.c b/kernel/exit.c
index 879ed6e1c883..0da2921b1e7f 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -698,7 +698,7 @@ reparent_thread(struct task_struct *p, struct task_struct *father, int traced)
         if (unlikely(traced)) {
                 /* Preserve ptrace links if someone else is tracing this child.  */
                 list_del_init(&p->ptrace_list);
-                if (p->parent != p->real_parent)
+                if (ptrace_reparented(p))
                         list_add(&p->ptrace_list, &p->real_parent->ptrace_children);
         } else {
                 /* If this child is being traced, then we're the one tracing it
@@ -865,8 +865,8 @@ static void exit_notify(struct task_struct *tsk, int group_dead)
          * only has special meaning to our real parent.
          */
         if (!task_detached(tsk) && thread_group_empty(tsk)) {
-                int signal = (tsk->parent == tsk->real_parent)
-                                ? tsk->exit_signal : SIGCHLD;
+                int signal = ptrace_reparented(tsk) ?
+                                SIGCHLD : tsk->exit_signal;
                 do_notify_parent(tsk, signal);
         } else if (tsk->ptrace) {
                 do_notify_parent(tsk, SIGCHLD);
@@ -1269,8 +1269,7 @@ static int wait_task_zombie(struct task_struct *p, int noreap,
                 return 0;
         }
 
-        /* traced means p->ptrace, but not vice versa */
-        traced = (p->real_parent != p->parent);
+        traced = ptrace_reparented(p);
 
         if (likely(!traced)) {
                 struct signal_struct *psig;