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[195.250.132.146]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43b6470393fsm30608008f8f.17.2026.03.23.05.40.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Mar 2026 05:40:11 -0700 (PDT) From: =?utf-8?q?Michal_Koutn=C3=BD?= Date: Mon, 23 Mar 2026 13:39:37 +0100 Subject: [PATCH v3 1/3] sched/rt: Skip group schedulable check with rt_group_sched=0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260323-sched-rert_groups-v3-1-1e7d5ed6b249@suse.com> References: <20260323-sched-rert_groups-v3-0-1e7d5ed6b249@suse.com> In-Reply-To: <20260323-sched-rert_groups-v3-0-1e7d5ed6b249@suse.com> To: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider Cc: linux-kernel@vger.kernel.org, K Prateek Nayak , =?utf-8?q?Michal_Koutn=C3=BD?= X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=1729; i=mkoutny@suse.com; h=from:subject:message-id; bh=ETkk6X1fHslEtzTthMQL4uiXn0e7TKA04ds5WgokxWM=; b=owGbwMvMwCVWZ8v0fMrtHxyMp9WSGDIPmsxtiruUMy9OSTRV+XHsy/mzfhteFrXKbO9a22kn7 P9Abj9zx0QWBjEuBksxRRYn4TzW+R9k3CxPd32BmcPKBDJEWqSBAQhYGPhyE/NKjXSM9Ey1DfUM gQwdIwYuTgGY6vdLGRl6O6xXXJQ7+FglxUvPXr3NX2H6ow+F7x2vRUmZpyS8vbmP4Z95zoSP2xi dzLU2sk3WWDfxKPfT6tjSXZdTT25wOXicxZ0HAA== X-Developer-Key: i=mkoutny@suse.com; a=openpgp; fpr=9F2AB6F1F2BBEE7621C1B620CFDED9A2FD1314F0 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=3D0 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=3D0 there is no (non-trivial) hierarchy of RT group= s, 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=3Dn. Fixes: 87f1fb77d87a6 ("sched: Add RT_GROUP WARN checks for non-root task_gr= oups") Signed-off-by: Michal Koutn=C3=BD --- kernel/sched/rt.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index f69e1f16d9238..37e6ce3604fd7 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -2676,9 +2676,6 @@ static int tg_rt_schedulable(struct task_group *tg, v= oid *data) tg->rt_bandwidth.rt_runtime && tg_has_rt_tasks(tg)) return -EBUSY; =20 - if (WARN_ON(!rt_group_sched_enabled() && tg !=3D &root_task_group)) - return -EBUSY; - total =3D to_ratio(period, runtime); =20 /* @@ -2822,6 +2819,8 @@ long sched_group_rt_period(struct task_group *tg) static int sched_rt_global_constraints(void) { int ret =3D 0; + if (!rt_group_sched_enabled()) + return ret; =20 mutex_lock(&rt_constraints_mutex); ret =3D __rt_schedulable(NULL, 0, 0); --=20 2.53.0