[PATCH] memcg: replace in_interrupt() by !in_task() in active_memcg()

[PATCH] memcg: replace in_interrupt() by !in_task() in active_memcg()

[Vasily Averin]

set_active_memcg() uses in_interrupt() check to select proper storage for
cgroup: pointer on task struct or per-cpu pointer.

It isn't fully correct: obsoleted in_interrupt() includes tasks with disabled BH.
It's better to use '!in_task()' instead.

Link: https://lkml.org/lkml/2021/7/26/487
Fixes: 37d5985c003d ("mm: kmem: prepare remote memcg charging infra for interrupt contexts")
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
---
 include/linux/sched/mm.h | 2 +-
 mm/memcontrol.c          | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index e24b1fe348e3..9dd071f78dba 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -306,7 +306,7 @@ set_active_memcg(struct mem_cgroup *memcg)
 {
 	struct mem_cgroup *old;
 
-	if (in_interrupt()) {
+	if (!in_task()) {
 		old = this_cpu_read(int_active_memcg);
 		this_cpu_write(int_active_memcg, memcg);
 	} else {
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ae1f5d0cb581..3ebf792ef2c0 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -905,7 +905,7 @@ EXPORT_SYMBOL(mem_cgroup_from_task);
 
 static __always_inline struct mem_cgroup *active_memcg(void)
 {
-	if (in_interrupt())
+	if (!in_task())
 		return this_cpu_read(int_active_memcg);
 	else
 		return current->active_memcg;
-- 
2.25.1

Re: [PATCH] memcg: replace in_interrupt() by !in_task() in active_memcg()

[Shakeel Butt]

On Mon, Jul 26, 2021 at 9:53 AM Vasily Averin <vvs@virtuozzo.com> wrote:
>
> set_active_memcg() uses in_interrupt() check to select proper storage for
> cgroup: pointer on task struct or per-cpu pointer.
>
> It isn't fully correct: obsoleted in_interrupt() includes tasks with disabled BH.
> It's better to use '!in_task()' instead.
>
> Link: https://lkml.org/lkml/2021/7/26/487
> Fixes: 37d5985c003d ("mm: kmem: prepare remote memcg charging infra for interrupt contexts")
> Signed-off-by: Vasily Averin <vvs@virtuozzo.com>

Thanks.

Reviewed-by: Shakeel Butt <shakeelb@google.com>