1 files changed, 18 insertions, 28 deletions

diff --git a/fs/exec.c b/fs/exec.c
index 0291a68a3626..3a79d97ac234 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -665,9 +665,7 @@ static int de_thread(struct task_struct *tsk)
          * and to assume its PID:
          */
         if (!thread_group_leader(current)) {
-                struct task_struct *parent;
                 struct dentry *proc_dentry1, *proc_dentry2;
-                unsigned long ptrace;
 
                 /*
                  * Wait for the thread group leader to be a zombie.
@@ -678,6 +676,18 @@ static int de_thread(struct task_struct *tsk)
                 while (leader->exit_state != EXIT_ZOMBIE)
                         yield();
 
+                /*
+                 * The only record we have of the real-time age of a
+                 * process, regardless of execs it's done, is start_time.
+                 * All the past CPU time is accumulated in signal_struct
+                 * from sister threads now dead.  But in this non-leader
+                 * exec, nothing survives from the original leader thread,
+                 * whose birth marks the true age of this process now.
+                 * When we take on its identity by switching to its PID, we
+                 * also take its birthdate (always earlier than our own).
+                 */
+                current->start_time = leader->start_time;
+
                 spin_lock(&leader->proc_lock);
                 spin_lock(&current->proc_lock);
                 proc_dentry1 = proc_pid_unhash(current);
@@ -692,22 +702,6 @@ static int de_thread(struct task_struct *tsk)
                  * two threads with a switched PID, and release
                  * the former thread group leader:
                  */
-                ptrace = leader->ptrace;
-                parent = leader->parent;
-                if (unlikely(ptrace) && unlikely(parent == current)) {
-                        /*
-                         * Joker was ptracing his own group leader,
-                         * and now he wants to be his own parent!
-                         * We can't have that.
-                         */
-                        ptrace = 0;
-                }
-
-                ptrace_unlink(current);
-                ptrace_unlink(leader);
-                remove_parent(current);
-                remove_parent(leader);
-
 
                 /* Become a process group leader with the old leader's pid.
                  * Note: The old leader also uses thispid until release_task
@@ -718,19 +712,15 @@ static int de_thread(struct task_struct *tsk)
                 attach_pid(current, PIDTYPE_PID,  current->pid);
                 attach_pid(current, PIDTYPE_PGID, current->signal->pgrp);
                 attach_pid(current, PIDTYPE_SID,  current->signal->session);
-                list_add_tail(&current->tasks, &init_task.tasks);
+                list_add_tail_rcu(&current->tasks, &init_task.tasks);
 
-                current->parent = current->real_parent = leader->real_parent;
-                leader->parent = leader->real_parent = child_reaper;
                 current->group_leader = current;
-                leader->group_leader = leader;
+                leader->group_leader = current;
 
-                add_parent(current);
-                add_parent(leader);
-                if (ptrace) {
-                        current->ptrace = ptrace;
-                        __ptrace_link(current, parent);
-                }
+                /* Reduce leader to a thread */
+                detach_pid(leader, PIDTYPE_PGID);
+                detach_pid(leader, PIDTYPE_SID);
+                list_del_init(&leader->tasks);
 
                 current->exit_signal = SIGCHLD;