[PATCH sched_ext/for-6.16] sched_ext: Remove cpu.weight / cpu.idle unimplemented warnings

Tejun Heo
2025-04-07T23:20:05Z

sched_ext generates warnings when cpu.weight / cpu.idle are set to
non-default values if the BPF scheduler doesn't implement weight support.
These warnings don't provide much value while adding constant annoyance. A
BPF scheduler may not implement any particular behavior and there's nothing
particularly special about missing cgroup weight support. Drop the warnings.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
kernel/sched/ext.c | 40 +---------------------------------------
1 file changed, 1 insertion(+), 39 deletions(-)

--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -3896,34 +3896,6 @@ bool scx_can_stop_tick(struct rq *rq)

DEFINE_STATIC_PERCPU_RWSEM(scx_cgroup_rwsem);
static bool scx_cgroup_enabled;
-static bool cgroup_warned_missing_weight;
-static bool cgroup_warned_missing_idle;
-
-static void scx_cgroup_warn_missing_weight(struct task_group *tg)
-{
- if (scx_enable_state() == SCX_DISABLED || cgroup_warned_missing_weight)
- return;
-
- if ((scx_ops.flags & SCX_OPS_HAS_CGROUP_WEIGHT) || !tg->css.parent)
- return;
-
- pr_warn("sched_ext: \"%s\" does not implement cgroup cpu.weight\n",
- scx_ops.name);
- cgroup_warned_missing_weight = true;
-}
-
-static void scx_cgroup_warn_missing_idle(struct task_group *tg)
-{
- if (!scx_cgroup_enabled || cgroup_warned_missing_idle)
- return;
-
- if (!tg->idle)
- return;
-
- pr_warn("sched_ext: \"%s\" does not implement cgroup cpu.idle\n",
- scx_ops.name);
- cgroup_warned_missing_idle = true;
-}

int scx_tg_online(struct task_group *tg)
{
@@ -3933,8 +3905,6 @@ int scx_tg_online(struct task_group *tg)

percpu_down_read(&scx_cgroup_rwsem);

- scx_cgroup_warn_missing_weight(tg);
-
if (scx_cgroup_enabled) {
if (SCX_HAS_OP(cgroup_init)) {
struct scx_cgroup_init_args args =
@@ -4072,9 +4042,7 @@ void scx_group_set_weight(struct task_gr

void scx_group_set_idle(struct task_group *tg, bool idle)
{
- percpu_down_read(&scx_cgroup_rwsem);
- scx_cgroup_warn_missing_idle(tg);
- percpu_up_read(&scx_cgroup_rwsem);
+ /* TODO: Implement ops->cgroup_set_idle() */
}

static void scx_cgroup_lock(void)
@@ -4268,9 +4236,6 @@ static int scx_cgroup_init(void)

percpu_rwsem_assert_held(&scx_cgroup_rwsem);

- cgroup_warned_missing_weight = false;
- cgroup_warned_missing_idle = false;
-
/*
* scx_tg_on/offline() are excluded through scx_cgroup_rwsem. If we walk
* cgroups and init, all online cgroups are initialized.
@@ -4280,9 +4245,6 @@ static int scx_cgroup_init(void)
struct task_group *tg = css_tg(css);
struct scx_cgroup_init_args args = { .weight = tg->scx_weight };

- scx_cgroup_warn_missing_weight(tg);
- scx_cgroup_warn_missing_idle(tg);
-
if ((tg->scx_flags &
(SCX_TG_ONLINE | SCX_TG_INITED)) != SCX_TG_ONLINE)
continue;