1 files changed, 118 insertions, 31 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index 2a9d98c641ac..d3ad54677f9c 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -52,6 +52,11 @@
 
 static void exit_mm(struct task_struct * tsk);
 
+static inline int task_detached(struct task_struct *p)
+{
+        return p->exit_signal == -1;
+}
+
 static void __unhash_process(struct task_struct *p)
 {
         nr_threads--;
@@ -160,7 +165,7 @@ repeat:
         zap_leader = 0;
         leader = p->group_leader;
         if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
-                BUG_ON(leader->exit_signal == -1);
+                BUG_ON(task_detached(leader));
                 do_notify_parent(leader, leader->exit_signal);
                 /*
                  * If we were the last child thread and the leader has
@@ -170,7 +175,7 @@ repeat:
                  * do_notify_parent() will have marked it self-reaping in
                  * that case.
                  */
-                zap_leader = (leader->exit_signal == -1);
+                zap_leader = task_detached(leader);
         }
 
         write_unlock_irq(&tasklist_lock);
@@ -329,13 +334,11 @@ void __set_special_pids(struct pid *pid)
         pid_t nr = pid_nr(pid);
 
         if (task_session(curr) != pid) {
-                detach_pid(curr, PIDTYPE_SID);
-                attach_pid(curr, PIDTYPE_SID, pid);
+                change_pid(curr, PIDTYPE_SID, pid);
                 set_task_session(curr, nr);
         }
         if (task_pgrp(curr) != pid) {
-                detach_pid(curr, PIDTYPE_PGID);
-                attach_pid(curr, PIDTYPE_PGID, pid);
+                change_pid(curr, PIDTYPE_PGID, pid);
                 set_task_pgrp(curr, nr);
         }
 }
@@ -557,6 +560,88 @@ void exit_fs(struct task_struct *tsk)
 
 EXPORT_SYMBOL_GPL(exit_fs);
 
+#ifdef CONFIG_MM_OWNER
+/*
+ * Task p is exiting and it owned mm, lets find a new owner for it
+ */
+static inline int
+mm_need_new_owner(struct mm_struct *mm, struct task_struct *p)
+{
+        /*
+         * If there are other users of the mm and the owner (us) is exiting
+         * we need to find a new owner to take on the responsibility.
+         */
+        if (!mm)
+                return 0;
+        if (atomic_read(&mm->mm_users) <= 1)
+                return 0;
+        if (mm->owner != p)
+                return 0;
+        return 1;
+}
+
+void mm_update_next_owner(struct mm_struct *mm)
+{
+        struct task_struct *c, *g, *p = current;
+
+retry:
+        if (!mm_need_new_owner(mm, p))
+                return;
+
+        read_lock(&tasklist_lock);
+        /*
+         * Search in the children
+         */
+        list_for_each_entry(c, &p->children, sibling) {
+                if (c->mm == mm)
+                        goto assign_new_owner;
+        }
+
+        /*
+         * Search in the siblings
+         */
+        list_for_each_entry(c, &p->parent->children, sibling) {
+                if (c->mm == mm)
+                        goto assign_new_owner;
+        }
+
+        /*
+         * Search through everything else. We should not get
+         * here often
+         */
+        do_each_thread(g, c) {
+                if (c->mm == mm)
+                        goto assign_new_owner;
+        } while_each_thread(g, c);
+
+        read_unlock(&tasklist_lock);
+        return;
+
+assign_new_owner:
+        BUG_ON(c == p);
+        get_task_struct(c);
+        /*
+         * The task_lock protects c->mm from changing.
+         * We always want mm->owner->mm == mm
+         */
+        task_lock(c);
+        /*
+         * Delay read_unlock() till we have the task_lock()
+         * to ensure that c does not slip away underneath us
+         */
+        read_unlock(&tasklist_lock);
+        if (c->mm != mm) {
+                task_unlock(c);
+                put_task_struct(c);
+                goto retry;
+        }
+        cgroup_mm_owner_callbacks(mm->owner, c);
+        mm->owner = c;
+        task_unlock(c);
+        put_task_struct(c);
+}
+#endif /* CONFIG_MM_OWNER */
+
 /*
  * Turn us into a lazy TLB process if we
  * aren't already..
@@ -596,6 +681,7 @@ static void exit_mm(struct task_struct * tsk)
         /* We don't want this task to be frozen prematurely */
         clear_freeze_flag(tsk);
         task_unlock(tsk);
+        mm_update_next_owner(mm);
         mmput(mm);
 }
 
@@ -610,7 +696,7 @@ reparent_thread(struct task_struct *p, struct task_struct *father, int traced)
         if (unlikely(traced)) {
                 /* Preserve ptrace links if someone else is tracing this child.  */
                 list_del_init(&p->ptrace_list);
-                if (p->parent != p->real_parent)
+                if (ptrace_reparented(p))
                         list_add(&p->ptrace_list, &p->real_parent->ptrace_children);
         } else {
                 /* If this child is being traced, then we're the one tracing it
@@ -634,18 +720,18 @@ reparent_thread(struct task_struct *p, struct task_struct *father, int traced)
         /* If this is a threaded reparent there is no need to
          * notify anyone anything has happened.
          */
-        if (p->real_parent->group_leader == father->group_leader)
+        if (same_thread_group(p->real_parent, father))
                 return;
 
         /* We don't want people slaying init.  */
-        if (p->exit_signal != -1)
+        if (!task_detached(p))
                 p->exit_signal = SIGCHLD;
 
         /* If we'd notified the old parent about this child's death,
          * also notify the new parent.
          */
         if (!traced && p->exit_state == EXIT_ZOMBIE &&
-            p->exit_signal != -1 && thread_group_empty(p))
+            !task_detached(p) && thread_group_empty(p))
                 do_notify_parent(p, p->exit_signal);
 
         kill_orphaned_pgrp(p, father);
@@ -698,18 +784,18 @@ static void forget_original_parent(struct task_struct *father)
                 } else {
                         /* reparent ptraced task to its real parent */
                         __ptrace_unlink (p);
-                        if (p->exit_state == EXIT_ZOMBIE && p->exit_signal != -1 &&
+                        if (p->exit_state == EXIT_ZOMBIE && !task_detached(p) &&
                             thread_group_empty(p))
                                 do_notify_parent(p, p->exit_signal);
                 }
 
                 /*
-                 * if the ptraced child is a zombie with exit_signal == -1
-                 * we must collect it before we exit, or it will remain
-                 * zombie forever since we prevented it from self-reap itself
-                 * while it was being traced by us, to be able to see it in wait4.
+                 * if the ptraced child is a detached zombie we must collect
+                 * it before we exit, or it will remain zombie forever since
+                 * we prevented it from self-reap itself while it was being
+                 * traced by us, to be able to see it in wait4.
                  */
-                if (unlikely(ptrace && p->exit_state == EXIT_ZOMBIE && p->exit_signal == -1))
+                if (unlikely(ptrace && p->exit_state == EXIT_ZOMBIE && task_detached(p)))
                         list_add(&p->ptrace_list, &ptrace_dead);
         }
 
@@ -766,29 +852,30 @@ static void exit_notify(struct task_struct *tsk, int group_dead)
          * we have changed execution domain as these two values started
          * the same after a fork.
          */
-        if (tsk->exit_signal != SIGCHLD && tsk->exit_signal != -1 &&
+        if (tsk->exit_signal != SIGCHLD && !task_detached(tsk) &&
             (tsk->parent_exec_id != tsk->real_parent->self_exec_id ||
-             tsk->self_exec_id != tsk->parent_exec_id)
-            && !capable(CAP_KILL))
+             tsk->self_exec_id != tsk->parent_exec_id) &&
+            !capable(CAP_KILL))
                 tsk->exit_signal = SIGCHLD;
 
-
         /* If something other than our normal parent is ptracing us, then
          * send it a SIGCHLD instead of honoring exit_signal.  exit_signal
          * only has special meaning to our real parent.
          */
-        if (tsk->exit_signal != -1 && thread_group_empty(tsk)) {
-                int signal = tsk->parent == tsk->real_parent ? tsk->exit_signal : SIGCHLD;
+        if (!task_detached(tsk) && thread_group_empty(tsk)) {
+                int signal = ptrace_reparented(tsk) ?
+                                SIGCHLD : tsk->exit_signal;
                 do_notify_parent(tsk, signal);
         } else if (tsk->ptrace) {
                 do_notify_parent(tsk, SIGCHLD);
         }
 
         state = EXIT_ZOMBIE;
-        if (tsk->exit_signal == -1 && likely(!tsk->ptrace))
+        if (task_detached(tsk) && likely(!tsk->ptrace))
                 state = EXIT_DEAD;
         tsk->exit_state = state;
 
+        /* mt-exec, de_thread() is waiting for us */
         if (thread_group_leader(tsk) &&
             tsk->signal->notify_count < 0 &&
             tsk->signal->group_exit_task)
@@ -1032,12 +1119,13 @@ asmlinkage long sys_exit(int error_code)
 NORET_TYPE void
 do_group_exit(int exit_code)
 {
+        struct signal_struct *sig = current->signal;
+
         BUG_ON(exit_code & 0x80); /* core dumps don't get here */
 
-        if (current->signal->flags & SIGNAL_GROUP_EXIT)
-                exit_code = current->signal->group_exit_code;
+        if (signal_group_exit(sig))
+                exit_code = sig->group_exit_code;
         else if (!thread_group_empty(current)) {
-                struct signal_struct *const sig = current->signal;
                 struct sighand_struct *const sighand = current->sighand;
                 spin_lock_irq(&sighand->siglock);
                 if (signal_group_exit(sig))
@@ -1089,7 +1177,7 @@ static int eligible_child(enum pid_type type, struct pid *pid, int options,
          * Do not consider detached threads that are
          * not ptraced:
          */
-        if (p->exit_signal == -1 && !p->ptrace)
+        if (task_detached(p) && !p->ptrace)
                 return 0;
 
         /* Wait for all children (clone and not) if __WALL is set;
@@ -1179,8 +1267,7 @@ static int wait_task_zombie(struct task_struct *p, int noreap,
                 return 0;
         }
 
-        /* traced means p->ptrace, but not vice versa */
-        traced = (p->real_parent != p->parent);
+        traced = ptrace_reparented(p);
 
         if (likely(!traced)) {
                 struct signal_struct *psig;
@@ -1281,9 +1368,9 @@ static int wait_task_zombie(struct task_struct *p, int noreap,
                  * If it's still not detached after that, don't release
                  * it now.
                  */
-                if (p->exit_signal != -1) {
+                if (!task_detached(p)) {
                         do_notify_parent(p, p->exit_signal);
-                        if (p->exit_signal != -1) {
+                        if (!task_detached(p)) {
                                 p->exit_state = EXIT_ZOMBIE;
                                 p = NULL;
                         }