sched, signals: fix the racy usage of ->signal in account_group_xxx/run_posix_cpu_timers

[linux-2.6-omap-h63xx.git] / kernel / sched_stats.h

diff --git a/kernel/sched_stats.h b/kernel/sched_stats.h
index ee71bec1da66a9dcb64d93a0e9934c15a155905b..7dbf72a2b02cf16f256af7655eb9b28c7f3ef856 100644 (file)
--- 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;