1 files changed, 53 insertions, 59 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index 1e77fc645317..6ed6a1d552b5 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -570,7 +570,7 @@ static void reparent_leader(struct task_struct *father, struct task_struct *p,
         if (same_thread_group(p->real_parent, father))
                 return;
 
-        /* We don't want people slaying init.  */
+        /* We don't want people slaying init. */
         p->exit_signal = SIGCHLD;
 
         /* If it has exited notify the new parent about this child's death. */
@@ -784,9 +784,10 @@ void do_exit(long code)
         exit_shm(tsk);
         exit_files(tsk);
         exit_fs(tsk);
+        if (group_dead)
+                disassociate_ctty(1);
         exit_task_namespaces(tsk);
         exit_task_work(tsk);
-        check_stack_usage();
         exit_thread();
 
         /*
@@ -797,21 +798,17 @@ void do_exit(long code)
          */
         perf_event_exit_task(tsk);
 
-        cgroup_exit(tsk, 1);
-
-        if (group_dead)
-                disassociate_ctty(1);
+        cgroup_exit(tsk);
 
         module_put(task_thread_info(tsk)->exec_domain->module);
 
-        proc_exit_connector(tsk);
-
         /*
          * FIXME: do that only when needed, using sched_exit tracepoint
          */
         flush_ptrace_hw_breakpoint(tsk);
 
         exit_notify(tsk, group_dead);
+        proc_exit_connector(tsk);
 #ifdef CONFIG_NUMA
         task_lock(tsk);
         mpol_put(tsk->mempolicy);
@@ -844,6 +841,7 @@ void do_exit(long code)
 
         validate_creds_for_do_exit(tsk);
 
+        check_stack_usage();
         preempt_disable();
         if (tsk->nr_dirtied)
                 __this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
@@ -1038,17 +1036,13 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
                 return wait_noreap_copyout(wo, p, pid, uid, why, status);
         }
 
+        traced = ptrace_reparented(p);
         /*
-         * Try to move the task's state to DEAD
-         * only one thread is allowed to do this:
+         * Move the task's state to DEAD/TRACE, only one thread can do this.
          */
-        state = xchg(&p->exit_state, EXIT_DEAD);
-        if (state != EXIT_ZOMBIE) {
-                BUG_ON(state != EXIT_DEAD);
+        state = traced && thread_group_leader(p) ? EXIT_TRACE : EXIT_DEAD;
+        if (cmpxchg(&p->exit_state, EXIT_ZOMBIE, state) != EXIT_ZOMBIE)
                 return 0;
-        }
-
-        traced = ptrace_reparented(p);
         /*
          * It can be ptraced but not reparented, check
          * thread_group_leader() to filter out sub-threads.
@@ -1109,7 +1103,7 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
 
         /*
          * Now we are sure this task is interesting, and no other
-         * thread can reap it because we set its state to EXIT_DEAD.
+         * thread can reap it because we its state == DEAD/TRACE.
          */
         read_unlock(&tasklist_lock);
 
@@ -1146,22 +1140,19 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
         if (!retval)
                 retval = pid;
 
-        if (traced) {
+        if (state == EXIT_TRACE) {
                 write_lock_irq(&tasklist_lock);
                 /* We dropped tasklist, ptracer could die and untrace */
                 ptrace_unlink(p);
-                /*
-                 * If this is not a sub-thread, notify the parent.
-                 * If parent wants a zombie, don't release it now.
-                 */
-                if (thread_group_leader(p) &&
-                    !do_notify_parent(p, p->exit_signal)) {
-                        p->exit_state = EXIT_ZOMBIE;
-                        p = NULL;
-                }
+
+                /* If parent wants a zombie, don't release it now */
+                state = EXIT_ZOMBIE;
+                if (do_notify_parent(p, p->exit_signal))
+                        state = EXIT_DEAD;
+                p->exit_state = state;
                 write_unlock_irq(&tasklist_lock);
         }
-        if (p != NULL)
+        if (state == EXIT_DEAD)
                 release_task(p);
 
         return retval;
@@ -1338,7 +1329,12 @@ static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
 static int wait_consider_task(struct wait_opts *wo, int ptrace,
                                 struct task_struct *p)
 {
-        int ret = eligible_child(wo, p);
+        int ret;
+
+        if (unlikely(p->exit_state == EXIT_DEAD))
+                return 0;
+
+        ret = eligible_child(wo, p);
         if (!ret)
                 return ret;
 
@@ -1356,33 +1352,44 @@ static int wait_consider_task(struct wait_opts *wo, int ptrace,
                 return 0;
         }
 
-        /* dead body doesn't have much to contribute */
-        if (unlikely(p->exit_state == EXIT_DEAD)) {
+        if (unlikely(p->exit_state == EXIT_TRACE)) {
                 /*
-                 * But do not ignore this task until the tracer does
-                 * wait_task_zombie()->do_notify_parent().
+                 * ptrace == 0 means we are the natural parent. In this case
+                 * we should clear notask_error, debugger will notify us.
                  */
-                if (likely(!ptrace) && unlikely(ptrace_reparented(p)))
+                if (likely(!ptrace))
                         wo->notask_error = 0;
                 return 0;
         }
 
-        /* slay zombie? */
-        if (p->exit_state == EXIT_ZOMBIE) {
+        if (likely(!ptrace) && unlikely(p->ptrace)) {
                 /*
-                 * A zombie ptracee is only visible to its ptracer.
-                 * Notification and reaping will be cascaded to the real
-                 * parent when the ptracer detaches.
+                 * If it is traced by its real parent's group, just pretend
+                 * the caller is ptrace_do_wait() and reap this child if it
+                 * is zombie.
+                 *
+                 * This also hides group stop state from real parent; otherwise
+                 * a single stop can be reported twice as group and ptrace stop.
+                 * If a ptracer wants to distinguish these two events for its
+                 * own children it should create a separate process which takes
+                 * the role of real parent.
                  */
-                if (likely(!ptrace) && unlikely(p->ptrace)) {
-                        /* it will become visible, clear notask_error */
-                        wo->notask_error = 0;
-                        return 0;
-                }
+                if (!ptrace_reparented(p))
+                        ptrace = 1;
+        }
 
+        /* slay zombie? */
+        if (p->exit_state == EXIT_ZOMBIE) {
                 /* we don't reap group leaders with subthreads */
-                if (!delay_group_leader(p))
-                        return wait_task_zombie(wo, p);
+                if (!delay_group_leader(p)) {
+                        /*
+                         * A zombie ptracee is only visible to its ptracer.
+                         * Notification and reaping will be cascaded to the
+                         * real parent when the ptracer detaches.
+                         */
+                        if (unlikely(ptrace) || likely(!p->ptrace))
+                                return wait_task_zombie(wo, p);
+                }
 
                 /*
                  * Allow access to stopped/continued state via zombie by
@@ -1408,19 +1415,6 @@ static int wait_consider_task(struct wait_opts *wo, int ptrace,
                         wo->notask_error = 0;
         } else {
                 /*
-                 * If @p is ptraced by a task in its real parent's group,
-                 * hide group stop/continued state when looking at @p as
-                 * the real parent; otherwise, a single stop can be
-                 * reported twice as group and ptrace stops.
-                 *
-                 * If a ptracer wants to distinguish the two events for its
-                 * own children, it should create a separate process which
-                 * takes the role of real parent.
-                 */
-                if (likely(!ptrace) && p->ptrace && !ptrace_reparented(p))
-                        return 0;
-
-                /*
                  * @p is alive and it's gonna stop, continue or exit, so
                  * there always is something to wait for.
                  */