Commit d6809c2f authored by Michal Koutný's avatar Michal Koutný Committed by Peter Zijlstra
Browse files

sched: Do not construct nor expose RT_GROUP_SCHED structures if disabled 



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: default avatarMichal Koutný <mkoutny@suse.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20250310170442.504716-8-mkoutny@suse.com
parent 277e0909

kernel/sched/core.c

+24 −12
Original line number Diff line number Diff line
@@ -9867,18 +9867,6 @@ 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",
@@ -9897,6 +9885,20 @@ 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 CONFIG_RT_GROUP_SCHED_DEFAULT_DISABLED

DEFINE_STATIC_KEY_FALSE(rt_group_sched);

# else
@@ -9919,6 +9921,16 @@ 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,

kernel/sched/rt.c

+9 −0
Original line number Diff line number Diff line
@@ -193,6 +193,9 @@ 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);

}
@@ -201,6 +204,9 @@ 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]);
@@ -245,6 +251,9 @@ 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;