[PATCH v4 11/13] task_isolation: net: don't flush backlog on CPUs running isolated tasks

Alex Belits
2020-07-22T14:58:55Z

From: Yuri Norov <ynorov@marvell.com>

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 <ynorov@marvell.com>
[abelits@marvell.com: use safe task_isolation_on_cpu() implementation]
Signed-off-by: Alex Belits <abelits@marvell.com>
---
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