2 files changed, 40 insertions, 29 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index c900aa530070..7531b1c28201 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -674,7 +674,7 @@ struct user_struct {
         struct task_group *tg;
 #ifdef CONFIG_SYSFS
         struct kobject kobj;
-        struct work_struct work;
+        struct delayed_work work;
 #endif
 #endif
 
diff --git a/kernel/user.c b/kernel/user.c
index 850e0ba41c1e..2c000e7132ac 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -75,21 +75,6 @@ static void uid_hash_remove(struct user_struct *up)
         put_user_ns(up->user_ns);
 }
 
-static struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent)
-{
-        struct user_struct *user;
-        struct hlist_node *h;
-
-        hlist_for_each_entry(user, h, hashent, uidhash_node) {
-                if (user->uid == uid) {
-                        atomic_inc(&user->__count);
-                        return user;
-                }
-        }
-
-        return NULL;
-}
-
 #ifdef CONFIG_USER_SCHED
 
 static void sched_destroy_user(struct user_struct *up)
@@ -119,6 +104,23 @@ static int sched_create_user(struct user_struct *up) { return 0; }
 
 #if defined(CONFIG_USER_SCHED) && defined(CONFIG_SYSFS)
 
+static struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent)
+{
+        struct user_struct *user;
+        struct hlist_node *h;
+
+        hlist_for_each_entry(user, h, hashent, uidhash_node) {
+                if (user->uid == uid) {
+                        /* possibly resurrect an "almost deleted" object */
+                        if (atomic_inc_return(&user->__count) == 1)
+                                cancel_delayed_work(&user->work);
+                        return user;
+                }
+        }
+
+        return NULL;
+}
+
 static struct kset *uids_kset; /* represents the /sys/kernel/uids/ directory */
 static DEFINE_MUTEX(uids_mutex);
 
@@ -283,12 +285,12 @@ int __init uids_sysfs_init(void)
         return uids_user_create(&root_user);
 }
 
-/* work function to remove sysfs directory for a user and free up
+/* delayed work function to remove sysfs directory for a user and free up
  * corresponding structures.
  */
 static void cleanup_user_struct(struct work_struct *w)
 {
-        struct user_struct *up = container_of(w, struct user_struct, work);
+        struct user_struct *up = container_of(w, struct user_struct, work.work);
         unsigned long flags;
         int remove_user = 0;
 
@@ -297,15 +299,12 @@ static void cleanup_user_struct(struct work_struct *w)
          */
         uids_mutex_lock();
 
-        local_irq_save(flags);
-
-        if (atomic_dec_and_lock(&up->__count, &uidhash_lock)) {
+        spin_lock_irqsave(&uidhash_lock, flags);
+        if (atomic_read(&up->__count) == 0) {
                 uid_hash_remove(up);
                 remove_user = 1;
-                spin_unlock_irqrestore(&uidhash_lock, flags);
-        } else {
-                local_irq_restore(flags);
         }
+        spin_unlock_irqrestore(&uidhash_lock, flags);
 
         if (!remove_user)
                 goto done;
@@ -331,16 +330,28 @@ done:
  */
 static void free_user(struct user_struct *up, unsigned long flags)
 {
-        /* restore back the count */
-        atomic_inc(&up->__count);
         spin_unlock_irqrestore(&uidhash_lock, flags);
-
-        INIT_WORK(&up->work, cleanup_user_struct);
-        schedule_work(&up->work);
+        INIT_DELAYED_WORK(&up->work, cleanup_user_struct);
+        schedule_delayed_work(&up->work, msecs_to_jiffies(1000));
 }
 
 #else   /* CONFIG_USER_SCHED && CONFIG_SYSFS */
 
+static struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent)
+{
+        struct user_struct *user;
+        struct hlist_node *h;
+
+        hlist_for_each_entry(user, h, hashent, uidhash_node) {
+                if (user->uid == uid) {
+                        atomic_inc(&user->__count);
+                        return user;
+                }
+        }
+
+        return NULL;
+}
+
 int uids_sysfs_init(void) { return 0; }
 static inline int uids_user_create(struct user_struct *up) { return 0; }
 static inline void uids_mutex_lock(void) { }