Thanks to kernel cmdline being available early, before any
cgroup hierarchy exists, we can achieve the RT_GROUP_SCHED boottime
disabling goal by simply skipping any creation (and destruction) of
RT_GROUP data and its exposure via RT attributes.
We can do this thanks to previously placed runtime guards that would
redirect all operations to root_task_group's data when RT_GROUP_SCHED
disabled.
Signed-off-by: Michal Koutný <mkoutny@xxxxxxxx>
---
kernel/sched/core.c | 36 ++++++++++++++++++++++++------------
kernel/sched/rt.c | 9 +++++++++
2 files changed, 33 insertions(+), 12 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 6e21e0885557d..300a1a83e1a3c 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9819,18 +9819,6 @@ static struct cftype cpu_legacy_files[] = {
.seq_show = cpu_cfs_local_stat_show,
},
#endif
-#ifdef CONFIG_RT_GROUP_SCHED
- {
- .name = "rt_runtime_us",
- .read_s64 = cpu_rt_runtime_read,
- .write_s64 = cpu_rt_runtime_write,
- },
- {
- .name = "rt_period_us",
- .read_u64 = cpu_rt_period_read_uint,
- .write_u64 = cpu_rt_period_write_uint,
- },
-#endif
#ifdef CONFIG_UCLAMP_TASK_GROUP
{
.name = "uclamp.min",
@@ -9849,6 +9837,20 @@ static struct cftype cpu_legacy_files[] = {
};
#ifdef CONFIG_RT_GROUP_SCHED
+static struct cftype rt_group_files[] = {
+ {
+ .name = "rt_runtime_us",
+ .read_s64 = cpu_rt_runtime_read,
+ .write_s64 = cpu_rt_runtime_write,
+ },
+ {
+ .name = "rt_period_us",
+ .read_u64 = cpu_rt_period_read_uint,
+ .write_u64 = cpu_rt_period_write_uint,
+ },
+ { } /* Terminate */
+};
+
# ifdef RT_GROUP_SCHED_DEFAULT_DISABLED
DEFINE_STATIC_KEY_FALSE(rt_group_sched);
# else
@@ -9871,6 +9873,16 @@ static int __init setup_rt_group_sched(char *str)
return 1;
}
__setup("rt_group_sched=", setup_rt_group_sched);
+
+static int __init cpu_rt_group_init(void)
+{
+ if (!rt_group_sched_enabled())
+ return 0;
+
+ WARN_ON(cgroup_add_legacy_cftypes(&cpu_cgrp_subsys, rt_group_files));
+ return 0;
+}
+subsys_initcall(cpu_rt_group_init);
#endif /* CONFIG_RT_GROUP_SCHED */
static int cpu_extra_stat_show(struct seq_file *sf,
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 161d91f7479b4..db7cdc82003bd 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -195,6 +195,9 @@ static inline struct rq *rq_of_rt_se(struct sched_rt_entity *rt_se)
void unregister_rt_sched_group(struct task_group *tg)
{
+ if (!rt_group_sched_enabled())
+ return;
+
if (tg->rt_se)
destroy_rt_bandwidth(&tg->rt_bandwidth);
}
@@ -203,6 +206,9 @@ void free_rt_sched_group(struct task_group *tg)
{
int i;
+ if (!rt_group_sched_enabled())
+ return;
+
for_each_possible_cpu(i) {
if (tg->rt_rq)
kfree(tg->rt_rq[i]);
@@ -247,6 +253,9 @@ int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
struct sched_rt_entity *rt_se;
int i;
+ if (!rt_group_sched_enabled())
+ return 1;
+
tg->rt_rq = kcalloc(nr_cpu_ids, sizeof(rt_rq), GFP_KERNEL);
if (!tg->rt_rq)
goto err;
--
2.47.1
