exit.c: unexport __set_special_pids()

Move __set_special_pids() from exit.c to sys.c close to its single caller
and make it static.

And rename it to set_special_pids(), another helper with this name has
gone away.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/sched.h

@@ -1950,8 +1950,6 @@ extern struct task_struct *find_task_by_vpid(pid_t nr);
 extern struct task_struct *find_task_by_pid_ns(pid_t nr,
 		struct pid_namespace *ns);
 
-extern void __set_special_pids(struct pid *pid);
-
 /* per-UID process charging. */
 extern struct user_struct * alloc_uid(kuid_t);
 static inline struct user_struct *get_uid(struct user_struct *u)

kernel/exit.c

@@ -312,17 +312,6 @@ kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
 	}
 }
 
-void __set_special_pids(struct pid *pid)
-{
-	struct task_struct *curr = current->group_leader;
-
-	if (task_session(curr) != pid)
-		change_pid(curr, PIDTYPE_SID, pid);
-
-	if (task_pgrp(curr) != pid)
-		change_pid(curr, PIDTYPE_PGID, pid);
-}
-
 /*
  * Let kernel threads use this to say that they allow a certain signal.
  * Must not be used if kthread was cloned with CLONE_SIGHAND.

kernel/sys.c

@@ -1309,6 +1309,17 @@ out:
 	return retval;
 }
 
+static void set_special_pids(struct pid *pid)
+{
+	struct task_struct *curr = current->group_leader;
+
+	if (task_session(curr) != pid)
+		change_pid(curr, PIDTYPE_SID, pid);
+
+	if (task_pgrp(curr) != pid)
+		change_pid(curr, PIDTYPE_PGID, pid);
+}
+
 SYSCALL_DEFINE0(setsid)
 {
 	struct task_struct *group_leader = current->group_leader;
@@ -1328,7 +1339,7 @@ SYSCALL_DEFINE0(setsid)
 		goto out;
 
 	group_leader->signal->leader = 1;
-	__set_special_pids(sid);
+	set_special_pids(sid);
 
 	proc_clear_tty(group_leader);