linux-kernel - [PATCH v5 7/9] task_isolation: don't interrupt CPUs with tick_nohz_full_kick

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Date:   Mon, 23 Nov 2020 17:58:22 +0000
From:   Alex Belits <abelits@...vell.com>
To:     "nitesh@...hat.com" <nitesh@...hat.com>,
        "frederic@...nel.org" <frederic@...nel.org>
CC:     Prasun Kapoor <pkapoor@...vell.com>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "trix@...hat.com" <trix@...hat.com>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "peterx@...hat.com" <peterx@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "mtosatti@...hat.com" <mtosatti@...hat.com>,
        "will@...nel.org" <will@...nel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "leon@...ebranch.com" <leon@...ebranch.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "pauld@...hat.com" <pauld@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: [PATCH v5 7/9] task_isolation: don't interrupt CPUs with
 tick_nohz_full_kick_cpu()

From: Yuri Norov <ynorov@...vell.com>

For nohz_full CPUs the desirable behavior is to receive interrupts
generated by tick_nohz_full_kick_cpu(). But for hard isolation it's
obviously not desirable because it breaks isolation.

This patch adds check for it.

Signed-off-by: Yuri Norov <ynorov@...vell.com>
[abelits@...vell.com: updated, only exclude CPUs running isolated tasks]
Signed-off-by: Alex Belits <abelits@...vell.com>
---
 kernel/time/tick-sched.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index a213952541db..6c8679e200f0 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -20,6 +20,7 @@
 #include <linux/sched/clock.h>
 #include <linux/sched/stat.h>
 #include <linux/sched/nohz.h>
+#include <linux/isolation.h>
 #include <linux/module.h>
 #include <linux/irq_work.h>
 #include <linux/posix-timers.h>
@@ -268,7 +269,8 @@ static void tick_nohz_full_kick(void)
  */
 void tick_nohz_full_kick_cpu(int cpu)
 {
-	if (!tick_nohz_full_cpu(cpu))
+	smp_rmb();
+	if (!tick_nohz_full_cpu(cpu) || task_isolation_on_cpu(cpu))
 		return;
 
 	irq_work_queue_on(&per_cpu(nohz_full_kick_work, cpu), cpu);
-- 
2.20.1