1 files changed, 36 insertions, 3 deletions

diff --git a/kernel/sched/stats.h b/kernel/sched/stats.h
index 2ef90a51ec5e..71bac979d5ee 100644
--- a/kernel/sched/stats.h
+++ b/kernel/sched/stats.h
@@ -162,6 +162,39 @@ sched_info_switch(struct task_struct *prev, struct task_struct *next)
  */
 
 /**
+ * cputimer_running - return true if cputimer is running
+ *
+ * @tsk:        Pointer to target task.
+ */
+static inline bool cputimer_running(struct task_struct *tsk)
+
+{
+        struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
+
+        if (!cputimer->running)
+                return false;
+
+        /*
+         * After we flush the task's sum_exec_runtime to sig->sum_sched_runtime
+         * in __exit_signal(), we won't account to the signal struct further
+         * cputime consumed by that task, even though the task can still be
+         * ticking after __exit_signal().
+         *
+         * In order to keep a consistent behaviour between thread group cputime
+         * and thread group cputimer accounting, lets also ignore the cputime
+         * elapsing after __exit_signal() in any thread group timer running.
+         *
+         * This makes sure that POSIX CPU clocks and timers are synchronized, so
+         * that a POSIX CPU timer won't expire while the corresponding POSIX CPU
+         * clock delta is behind the expiring timer value.
+         */
+        if (unlikely(!tsk->sighand))
+                return false;
+
+        return true;
+}
+
+/**
  * account_group_user_time - Maintain utime for a thread group.
  *
  * @tsk:        Pointer to task structure.
@@ -176,7 +209,7 @@ static inline void account_group_user_time(struct task_struct *tsk,
 {
         struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
 
-        if (!cputimer->running)
+        if (!cputimer_running(tsk))
                 return;
 
         raw_spin_lock(&cputimer->lock);
@@ -199,7 +232,7 @@ static inline void account_group_system_time(struct task_struct *tsk,
 {
         struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
 
-        if (!cputimer->running)
+        if (!cputimer_running(tsk))
                 return;
 
         raw_spin_lock(&cputimer->lock);
@@ -222,7 +255,7 @@ static inline void account_group_exec_runtime(struct task_struct *tsk,
 {
         struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
 
-        if (!cputimer->running)
+        if (!cputimer_running(tsk))
                 return;
 
         raw_spin_lock(&cputimer->lock);