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, Thomas Gleixner , dschatzberg@meta.com, peterz@infradead.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev Date: Tue, 24 Feb 2026 00:36:27 +0100 In-Reply-To: <80f657156fb2d32d8fe246e65e9ac8bf9d7cfbd5.camel@web.de> References: <20260219164648.3014-1-spasswolf@web.de> <594b9094ab76acf9e73cad8fca9c9efd6f75a980.camel@web.de> <20260219195851.7a7bd1b2@fedora> <1d56c93ee93334b9d320c93d255d7548f4497836.camel@web.de> <20260220104420.54610b04@gandalf.local.home> <20260223032257.4e6db467@fedora> <80f657156fb2d32d8fe246e65e9ac8bf9d7cfbd5.camel@web.de> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.56.2-0+deb13u1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:TnKL/4YrtRaqutj370i1yz7T6v4g+aua8XZpqm0YoJ/wX50lqIU mLCOUhk5UwRQ94Q2t83iAiKAggZIgONvx44l3pbJr25R1lPK8bPo+zi5j6G+leaQW51Wpgv 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but got no output). This is the debug patch (for v6.19): commit 655ad0d7ce2d03b1b8bfbc2a3e6c36b46a4604c5 Author: Bert Karwatzki Date: Mon Feb 23 21:49:47 2026 +0100 cgroup: add printk() cgroup_task_dead for PREEMPT_RT =20 Signed-off-by: Bert Karwatzki diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 5f0d33b04910..16bb40df5dd0 100644 =2D-- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -7029,6 +7029,7 @@ static void cgrp_dead_tasks_iwork_fn(struct irq_work= *iwork) { struct llist_node *lnode; struct task_struct *task, *next; + printk(KERN_INFO "%s:\n", __func__); =20 lnode =3D llist_del_all(this_cpu_ptr(&cgrp_dead_tasks)); llist_for_each_entry_safe(task, next, lnode, cg_dead_lnode) { @@ -7050,6 +7051,7 @@ static void __init cgroup_rt_init(void) =20 void cgroup_task_dead(struct task_struct *task) { + printk(KERN_INFO "%s: task =3D %s\n", __func__, task->comm); get_task_struct(task); llist_add(&task->cg_dead_lnode, this_cpu_ptr(&cgrp_dead_tasks)); irq_work_queue(this_cpu_ptr(&cgrp_dead_tasks_iwork)); This is the output captured via netconsole after rebooting via # echo reboot > /dev/kmsg && reboot 2026-02-24T00:17:38.836655+01:00 localhost 12,5335,211298089,-,caller=3DT3= 211;reboot=20 2026-02-24T00:17:38.848658+01:00 localhost 6,5336,211309667,-,caller=3DT0;= cgroup_task_dead: task =3D reboot 2026-02-24T00:17:38.848658+01:00 localhost 6,5337,211310223,-,caller=3DT50= ;cgrp_dead_tasks_iwork_fn:=20 2026-02-24T00:17:38.852694+01:00 localhost 6,5338,211313770,-,caller=3DT0;= cgroup_task_dead: task =3D gmain 2026-02-24T00:17:38.852694+01:00 localhost 6,5339,211313776,-,caller=3DT0;= cgroup_task_dead: task =3D xfce4-sess:cs0 2026-02-24T00:17:38.852694+01:00 localhost 6,5340,211313798,-,caller=3DT0;= cgroup_task_dead: task =3D xfce4-sess:sh0 2026-02-24T00:17:38.852694+01:00 localhost 6,5341,211313810,-,caller=3DT0;= cgroup_task_dead: task =3D xfce4-:sh_opt0 2026-02-24T00:17:38.852694+01:00 localhost 6,5342,211313830,-,caller=3DT0;= cgroup_task_dead: task =3D xfce4-:traceq0 2026-02-24T00:17:38.852694+01:00 localhost 6,5343,211313840,-,caller=3DT0;= cgroup_task_dead: task =3D pool-spawner 2026-02-24T00:17:38.852694+01:00 localhost 6,5344,211313839,-,caller=3DT0;= cgroup_task_dead: task =3D xfce4-:traceq0 2026-02-24T00:17:38.852694+01:00 localhost 6,5345,211313868,-,caller=3DT0;= cgroup_task_dead: task =3D xfce4-session 2026-02-24T00:17:38.852694+01:00 localhost 6,5346,211313871,-,caller=3DT0;= cgroup_task_dead: task =3D xfce4-:traceq0 2026-02-24T00:17:38.852694+01:00 localhost 6,5347,211313874,-,caller=3DT0;= cgroup_task_dead: task =3D xfce4-s:disk$0 [...] Here comes the part which shows the delay (I did not remove any message he= re): 2026-02-24T00:17:40.964180+01:00 localhost 6,6838,213423568,-,caller=3DT0;= cgroup_task_dead: task =3D (sd-close) 2026-02-24T00:17:40.964244+01:00 localhost 6,6839,213423756,-,caller=3DT0;= cgroup_task_dead: task =3D systemctl 2026-02-24T00:17:40.964576+01:00 localhost 6,6840,213424221,-,caller=3DT34= ;cgrp_dead_tasks_iwork_fn:=20 2026-02-24T00:17:40.964649+01:00 localhost 6,6841,213424221,-,caller=3DT23= ;cgrp_dead_tasks_iwork_fn:=20 2026-02-24T00:17:40.964969+01:00 localhost 6,6842,213424435,-,caller=3DT0;= cgroup_task_dead: task =3D (sd-close) 2026-02-24T00:17:40.965057+01:00 localhost 6,6843,213425219,-,caller=3DT50= ;cgrp_dead_tasks_iwork_fn:=20 2026-02-24T00:17:44.025094+01:00 localhost 6,6844,216485806,-,caller=3DT0;= cgroup_task_dead: task =3D (udev-worker) 2026-02-24T00:17:44.025094+01:00 localhost 6,6845,216485810,-,caller=3DT0;= cgroup_task_dead: task =3D (udev-worker) 2026-02-24T00:17:44.025387+01:00 localhost 6,6846,216485816,-,caller=3DT0;= cgroup_task_dead: task =3D (udev-worker) 2026-02-24T00:17:44.025642+01:00 localhost 6,6847,216486228,-,caller=3DT66= ;cgrp_dead_tasks_iwork_fn:=20 2026-02-24T00:17:44.025718+01:00 localhost 6,6848,216486239,-,caller=3DT12= 2;cgrp_dead_tasks_iwork_fn:=20 2026-02-24T00:17:44.025923+01:00 localhost 6,6849,216486239,-,caller=3DT82= ;cgrp_dead_tasks_iwork_fn:=20 2026-02-24T00:19:11.070444+01:00 localhost 6,6850,303512419,-,caller=3DT0;= cgroup_task_dead: task =3D systemd 2026-02-24T00:19:11.070444+01:00 localhost 6,6851,303513238,-,caller=3DT34= ;cgrp_dead_tasks_iwork_fn:=20 2026-02-24T00:19:11.070725+01:00 localhost 6,6852,303513728,-,caller=3DT0;= cgroup_task_dead: task =3D (sd-pam) 2026-02-24T00:19:11.070888+01:00 localhost 6,6853,303514010,-,caller=3DT0;= cgroup_task_dead: task =3D (sd-close) 2026-02-24T00:19:11.071192+01:00 localhost 6,6854,303514221,-,caller=3DT90= ;cgrp_dead_tasks_iwork_fn:=20 2026-02-24T00:19:11.071291+01:00 localhost 6,6855,303514238,-,caller=3DT50= ;cgrp_dead_tasks_iwork_fn:=20 2026-02-24T00:19:11.071626+01:00 localhost 6,6856,303514629,-,caller=3DT0;= cgroup_task_dead: task =3D (sd-close) 2026-02-24T00:19:11.072139+01:00 localhost 6,6857,303515237,-,caller=3DT50= ;cgrp_dead_tasks_iwork_fn:=20 2026-02-24T00:19:11.107473+01:00 localhost 6,6858,303549400,-,caller=3DT0;= cgroup_task_dead: task =3D psimon 2026-02-24T00:19:11.107473+01:00 localhost 6,6859,303550244,-,caller=3DT66= ;cgrp_dead_tasks_iwork_fn: [...] I've tried this several times and the function calls just before the delay= are always the same. Bert Karwatzki