linux-kernel - [PATCH v2] sched/cputime: exclude ktimers threads in irqtime_account

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Message-ID: <20231130094130.GA12116@didi-ThinkCentre-M930t-N000>
Date:   Thu, 30 Nov 2023 17:41:47 +0800
From:   tiozhang <tiozhang@...iglobal.com>
To:     <rostedt@...dmis.org>, <bigeasy@...utronix.de>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <peterz@...radead.org>,
        <juri.lelli@...hat.com>, <vincent.guittot@...aro.org>
CC:     <linux-kernel@...r.kernel.org>, <dietmar.eggemann@....com>,
        <rostedt@...dmis.org>, <bsegall@...gle.com>, <mgorman@...e.de>,
        <bristot@...hat.com>, <vschneid@...hat.com>,
        <zyhtheonly@...il.com>, <tiozhang@...iglobal.com>,
        <zyhtheonly@...h.net>
Subject: [PATCH v2] sched/cputime: exclude ktimers threads in
 irqtime_account_irq

In CONFIG_PREEMPT_RT kernel, ktimers also calls __do_softirq,
so when accounting CPUTIME_SOFTIRQ, ktimers need to be excluded
as well as ksoftirqd.
Also add this_cpu_ktimers to keep consistency with this_cpu_ksoftirqd.

Signed-off-by: tiozhang <tiozhang@...iglobal.com>
---
 include/linux/interrupt.h | 5 +++++
 kernel/sched/cputime.c    | 3 ++-
 2 files changed, 7 insertions(+), 1 deletion(-)

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..fd3610353e12 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);
 }
 
-- 
2.17.1