Merge git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6

1 files changed, 11 insertions, 4 deletions

diff --git a/kernel/sched_stats.h b/kernel/sched_stats.h
index ee71bec1da66..7dbf72a2b02c 100644
--- a/kernel/sched_stats.h
+++ b/kernel/sched_stats.h
@@ -298,9 +298,11 @@ static inline void account_group_user_time(struct task_struct *tsk,
 {
         struct signal_struct *sig;
 
-        sig = tsk->signal;
-        if (unlikely(!sig))
+        /* tsk == current, ensure it is safe to use ->signal */
+        if (unlikely(tsk->exit_state))
                 return;
+
+        sig = tsk->signal;
         if (sig->cputime.totals) {
                 struct task_cputime *times;
 
@@ -325,9 +327,11 @@ static inline void account_group_system_time(struct task_struct *tsk,
 {
         struct signal_struct *sig;
 
-        sig = tsk->signal;
-        if (unlikely(!sig))
+        /* tsk == current, ensure it is safe to use ->signal */
+        if (unlikely(tsk->exit_state))
                 return;
+
+        sig = tsk->signal;
         if (sig->cputime.totals) {
                 struct task_cputime *times;
 
@@ -353,8 +357,11 @@ static inline void account_group_exec_runtime(struct task_struct *tsk,
         struct signal_struct *sig;
 
         sig = tsk->signal;
+        /* see __exit_signal()->task_rq_unlock_wait() */
+        barrier();
         if (unlikely(!sig))
                 return;
+
         if (sig->cputime.totals) {
                 struct task_cputime *times;