cgroup: keep zombies associated with their original cgroups

[mirror_ubuntu-zesty-kernel.git] / kernel / cgroup.c

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index ba7b3284c2e4cb1b33fe5d891e8dbacb5b6bc1c4..918658497625389c21691357c83ec284622e783d 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -5379,14 +5379,34 @@ int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
                        seq_printf(m, "%sname=%s", count ? "," : "",
                                   root->name);
                seq_putc(m, ':');
+
                cgrp = task_cgroup_from_root(tsk, root);
-               path = cgroup_path(cgrp, buf, PATH_MAX);
-               if (!path) {
-                       retval = -ENAMETOOLONG;
-                       goto out_unlock;
+
+               /*
+                * On traditional hierarchies, all zombie tasks show up as
+                * belonging to the root cgroup.  On the default hierarchy,
+                * while a zombie doesn't show up in "cgroup.procs" and
+                * thus can't be migrated, its /proc/PID/cgroup keeps
+                * reporting the cgroup it belonged to before exiting.  If
+                * the cgroup is removed before the zombie is reaped,
+                * " (deleted)" is appended to the cgroup path.
+                */
+               if (cgroup_on_dfl(cgrp) || !(tsk->flags & PF_EXITING)) {
+                       path = cgroup_path(cgrp, buf, PATH_MAX);
+                       if (!path) {
+                               retval = -ENAMETOOLONG;
+                               goto out_unlock;
+                       }
+               } else {
+                       path = "/";
                }
+
                seq_puts(m, path);
-               seq_putc(m, '\n');
+
+               if (cgroup_on_dfl(cgrp) && cgroup_is_dead(cgrp))
+                       seq_puts(m, " (deleted)\n");
+               else
+                       seq_putc(m, '\n');
        }
 
        retval = 0;
@@ -5593,7 +5613,6 @@ void cgroup_exit(struct task_struct *tsk)
 {
        struct cgroup_subsys *ss;
        struct css_set *cset;
-       bool put_cset = false;
        int i;
 
        /*
@@ -5606,22 +5625,20 @@ void cgroup_exit(struct task_struct *tsk)
                spin_lock_bh(&css_set_lock);
                css_set_move_task(tsk, cset, NULL, false);
                spin_unlock_bh(&css_set_lock);
-               put_cset = true;
+       } else {
+               get_css_set(cset);
        }
 
-       /* Reassign the task to the init_css_set. */
-       RCU_INIT_POINTER(tsk->cgroups, &init_css_set);
-
        /* see cgroup_post_fork() for details */
-       for_each_subsys_which(ss, i, &have_exit_callback) {
-               struct cgroup_subsys_state *old_css = cset->subsys[i];
-               struct cgroup_subsys_state *css = task_css(tsk, i);
+       for_each_subsys_which(ss, i, &have_exit_callback)
+               ss->exit(tsk);
+}
 
-               ss->exit(css, old_css, tsk);
-       }
+void cgroup_free(struct task_struct *task)
+{
+       struct css_set *cset = task_css_set(task);
 
-       if (put_cset)
-               put_css_set(cset);
+       put_css_set(cset);
 }
 
 static void check_for_release(struct cgroup *cgrp)