[PATCH v3] sched/cputime: let ktimers align with ksoftirqd in accounting CPUTIME_SOFTIRQ

[tiozhang <tiozhang@didiglobal.com>]

In CONFIG_PREEMPT_RT kernel, ktimers also calls __do_softirq,
so when accounting CPUTIME_SOFTIRQ, ktimers need to be accounted the same
as ksoftirqd.

Signed-off-by: tiozhang <tiozhang@didiglobal.com>
---
 include/linux/interrupt.h | 5 +++++
 kernel/sched/cputime.c    | 6 ++++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index a5091ac97fc6..a88646acaf3f 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -621,6 +621,11 @@ static inline unsigned int local_pending_timers(void)
         return __this_cpu_read(pending_timer_softirq);
 }
 
+static inline struct task_struct *this_cpu_ktimers(void)
+{
+	return this_cpu_read(timersd);
+}
+
 #else
 static inline void raise_timer_softirq(void)
 {
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index af7952f12e6c..2393c533314f 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -73,7 +73,8 @@ void irqtime_account_irq(struct task_struct *curr, unsigned int offset)
 	 */
 	if (pc & HARDIRQ_MASK)
 		irqtime_account_delta(irqtime, delta, CPUTIME_IRQ);
-	else if ((pc & SOFTIRQ_OFFSET) && curr != this_cpu_ksoftirqd())
+	else if (((pc & SOFTIRQ_OFFSET) && curr != this_cpu_ksoftirqd() &&
+		  (!IS_ENABLED(CONFIG_PREEMPT_RT) || curr != this_cpu_ktimers()))
 		irqtime_account_delta(irqtime, delta, CPUTIME_SOFTIRQ);
 }
 
@@ -391,7 +392,8 @@ static void irqtime_account_process_tick(struct task_struct *p, int user_tick,
 
 	cputime -= other;
 
-	if (this_cpu_ksoftirqd() == p) {
+	if (this_cpu_ksoftirqd() == p ||
+	   (IS_ENABLED(CONFIG_PREEMPT_RT) && this_cpu_ktimers() == p)) {
 		/*
 		 * ksoftirqd time do not get accounted in cpu_softirq_time.
 		 * So, we have to handle it separately here.
-- 
2.17.1