From: Yuri Norov <redacted>

If CPU runs isolated task, there's no any backlog on it, and
so we don't need to flush it. Currently flush_all_backlogs()
enqueues corresponding work on all CPUs including ones that run
isolated tasks. It leads to breaking task isolation for nothing.

In this patch, backlog flushing is enqueued only on non-isolated CPUs.

Signed-off-by: Yuri Norov <redacted>
[abelits@marvell.com: use safe task_isolation_on_cpu() implementation]
Signed-off-by: Alex Belits <redacted>
---
 net/core/dev.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 90b59fc50dc9..83a282f7453d 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c

@@ -74,6 +74,7 @@
 #include <linux/cpu.h>
 #include <linux/types.h>
 #include <linux/kernel.h>
+#include <linux/isolation.h>
 #include <linux/hash.h>
 #include <linux/slab.h>
 #include <linux/sched.h>

@@ -5624,9 +5625,13 @@ static void flush_all_backlogs(void)
 
 	get_online_cpus();
 
-	for_each_online_cpu(cpu)
+	smp_rmb();
+	for_each_online_cpu(cpu) {
+		if (task_isolation_on_cpu(cpu))
+			continue;
 		queue_work_on(cpu, system_highpri_wq,
 			      per_cpu_ptr(&flush_works, cpu));
+	}
 
 	for_each_online_cpu(cpu)
 		flush_work(per_cpu_ptr(&flush_works, cpu));

-- 
2.26.2

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