From: Michal Koutný Date: Mon, 23 Mar 2026 12:39:37 +0000 (+0100) Subject: sched/rt: Skip group schedulable check with rt_group_sched=0 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=8b016dcec9365675be81d26be88f2c09cf983bd4;p=thirdparty%2Fkernel%2Flinux.git sched/rt: Skip group schedulable check with rt_group_sched=0 The warning from the commit 87f1fb77d87a6 ("sched: Add RT_GROUP WARN checks for non-root task_groups") is wrong -- it assumes that only task_groups with rt_rq are traversed, however, the schedulability check would iterate all task_groups even when rt_group_sched=0 is disabled at boot time but some non-root task_groups exist. The schedulability check is supposed to validate: a) that children don't overcommit its parent, b) no RT task group overcommits global RT limit. but with rt_group_sched=0 there is no (non-trivial) hierarchy of RT groups, therefore skip the validation altogether. Otherwise, writes to the global sched_rt_runtime_us knob will be rejected with incorrect validation error. This fix is immaterial with CONFIG_RT_GROUP_SCHED=n. Fixes: 87f1fb77d87a6 ("sched: Add RT_GROUP WARN checks for non-root task_groups") Signed-off-by: Michal Koutný Signed-off-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/20260323-sched-rert_groups-v3-1-1e7d5ed6b249@suse.com --- diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index a48e867949136..893e54dab13ef 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -2690,9 +2690,6 @@ static int tg_rt_schedulable(struct task_group *tg, void *data) tg->rt_bandwidth.rt_runtime && tg_has_rt_tasks(tg)) return -EBUSY; - if (WARN_ON(!rt_group_sched_enabled() && tg != &root_task_group)) - return -EBUSY; - total = to_ratio(period, runtime); /* @@ -2836,6 +2833,8 @@ long sched_group_rt_period(struct task_group *tg) static int sched_rt_global_constraints(void) { int ret = 0; + if (!rt_group_sched_enabled()) + return ret; mutex_lock(&rt_constraints_mutex); ret = __rt_schedulable(NULL, 0, 0);