# \[PATCH v4 10/13\] task\_isolation: don't interrupt CPUs with tick\_nohz\_full\_kick\_cpu()

- From: Alex Belits \<hidden\>
- Date: 2020-07-22 14:58:04 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2020/07/6046070
- Thread: https://ratatoskr.run/linux-api/2020/07/6046049/t.md

```text
From: Yuri Norov <redacted>

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 <redacted>
[abelits@marvell.com: updated, only exclude CPUs running isolated tasks]
Signed-off-by: Alex Belits <redacted>
---
 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 6e4cd8459f05..2f82a6daf8fc 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);
-- 
2.26.2

```