Re: [PATCH v4 11/13] task_isolation: net: don't flush backlog on CPUs running isolated tasks
From: Frederic Weisbecker <frederic@kernel.org>
Date: 2020-10-01 14:47:36
Also in:
linux-api, linux-arch, linux-arm-kernel, lkml
On Wed, Jul 22, 2020 at 02:58:24PM +0000, Alex Belits wrote:
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.
What guarantees that we have no backlog on it?
quoted hunk ↗ jump to hunk
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();
What is it ordering?
+ 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));Thanks.