Merge branch 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  cpuset: fix regression when failed to generate sched domains
  sched, signals: fix the racy usage of ->signal in account_group_xxx/run_posix_cpu_timers
  sched: fix kernel warning on /proc/sched_debug access
  sched: correct sched-rt-group.txt pathname in init/Kconfig

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;