On Fri, Dec 04, 2020 at 12:54:29AM +0000, Alex Belits wrote:

On Wed, 2020-12-02 at 14:20 +0000, Mark Rutland wrote:

quoted

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On Mon, Nov 23, 2020 at 05:58:22PM +0000, Alex Belits wrote:

quoted

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 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();

What does this barrier pair with? The commit message doesn't mention
it,
and it's not clear in-context.

With barriers in task_isolation_kernel_enter()
and task_isolation_exit_to_user_mode().

Please add a comment in the code as to what it pairs with.

Thanks,
Mark.