1 files changed, 29 insertions, 5 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 2357733a0a80..88e863460726 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -141,15 +141,36 @@ enum {
         CGRP_WAIT_ON_RMDIR,
 };
 
+/* which pidlist file are we talking about? */
+enum cgroup_filetype {
+        CGROUP_FILE_PROCS,
+        CGROUP_FILE_TASKS,
+};
+
+/*
+ * A pidlist is a list of pids that virtually represents the contents of one
+ * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
+ * a pair (one each for procs, tasks) for each pid namespace that's relevant
+ * to the cgroup.
+ */
 struct cgroup_pidlist {
-        /* protects the other fields */
-        struct rw_semaphore mutex;
+        /*
+         * used to find which pidlist is wanted. doesn't change as long as
+         * this particular list stays in the list.
+         */
+        struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
         /* array of xids */
         pid_t *list;
         /* how many elements the above list has */
         int length;
         /* how many files are using the current array */
         int use_count;
+        /* each of these stored in a list by its cgroup */
+        struct list_head links;
+        /* pointer to the cgroup we belong to, for list removal purposes */
+        struct cgroup *owner;
+        /* protects the other fields */
+        struct rw_semaphore mutex;
 };
 
 struct cgroup {
@@ -190,9 +211,12 @@ struct cgroup {
          */
         struct list_head release_list;
 
-        /* we will have two separate pidlists, one for pids (the tasks file)
-         * and one for tgids (the procs file). */
-        struct cgroup_pidlist tasks, procs;
+        /*
+         * list of pidlists, up to two for each namespace (one for procs, one
+         * for tasks); created on demand.
+         */
+        struct list_head pidlists;
+        struct mutex pidlist_mutex;
 
         /* For RCU-protected deletion */
         struct rcu_head rcu_head;