From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1F27D1F4CB3 for ; Mon, 15 Jun 2026 03:54:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781495696; cv=none; b=gybcxPAQiY/yg5CRdh0xMqGTAjLklR4lEHVFrUS67DnfR6AqAZqJlWpjlK2bwdtz8y+kIx9JekKv2xxji6ktxljmFQtmaCtopeP+xvUW39qBKeTCCRGJZOKuJUlw+nlHnm9GVnmmGebBWLFosuk7Q2ytUnzbwLBR17RzgEmkiJ0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781495696; c=relaxed/simple; bh=VZ3qAQFH0Ny/I7BShf4jEkeD4Q4pb8h5/gQVz7KJN7g=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=VxXF7c6Bf01yUxB9RDUgeivG2ZPiQ87ccx9Ya91Rz6GEPe0Fap0U5gbDbKKTQiExO2332c8CAcnodfhdTnNphdVkXVPo1buxxKVRDpplOhOo8LRNPMrFGe0ZnqWjmKma+eBKFqk7WhbVuAI0Yw85j+CSedDGewyUp6yN9nEQk20= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Ppdrt53X; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Ppdrt53X" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5F0AB1F000E9; Mon, 15 Jun 2026 03:54:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1781495695; bh=s4KnHiXoFGoVIs/fBRfD0dKcr8qGMa1uVwfctmbwhU0=; h=Subject:To:Cc:From:Date; b=Ppdrt53XpiWmuOLaCHScNqzKJ0fZeKvkadnYCx+IuVfoTm5UfAz4X4qsMNiDhh0s1 w05SOuibFRZ3QR4X6tCxZm49WdxBUOmGdyndpWL8XPo88SQY/aHI+aMQM4S+QN5sCx sv7EI4qrjyPwTEDXP4J+ATmWdmT7xaaSJe6iNzqQ= Subject: FAILED: patch "[PATCH] sched_ext: Don't warn on NULL cgrp_moving_from in" failed to apply to 7.0-stable tree To: tj@kernel.org,arighi@nvidia.com,mfleming@cloudflare.com Cc: From: Date: Mon, 15 Jun 2026 05:53:53 +0200 Message-ID: <2026061552-lividly-railcar-9730@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 7.0-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-7.0.y git checkout FETCH_HEAD git cherry-pick -x 02e545c4297a26dbbc41df81b831e7f605bcd306 # git commit -s git send-email --to '' --in-reply-to '2026061552-lividly-railcar-9730@gregkh' --subject-prefix 'PATCH 7.0.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 02e545c4297a26dbbc41df81b831e7f605bcd306 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 1 Jun 2026 09:22:37 -1000 Subject: [PATCH] sched_ext: Don't warn on NULL cgrp_moving_from in scx_cgroup_move_task() A WARN fires when systemd's user manager writes "+cpu +memory +pids" to its own subtree_control while a sched_ext scheduler is loaded: WARNING: at kernel/sched/ext.c:3227 scx_cgroup_move_task+0xa8/0xb0 scx_cgroup_move_task+0xa8/0xb0 sched_move_task+0x134/0x290 cpu_cgroup_attach+0x39/0x70 cgroup_migrate_execute+0x37d/0x450 cgroup_update_dfl_csses+0x1e3/0x270 cgroup_subtree_control_write+0x3e7/0x440 scx_cgroup_can_attach() arms cgrp_moving_from only when a task's cpu cgroup changes. It can still be NULL when scx_cgroup_move_task() runs, through this sequence: Step Result --------------------------------- ---------------------------------- 1. cpu enabled on cgroup G cpu css = A 2. cpu toggled off then on for G A killed, B created (same cgroup) 3. an exiting task keeps A alive migration skips it, A now stale 4. +memory migrates G stale A vs current B pulls cpu in 5. cpu attach runs for all tasks hits a live, cpu-unchanged task 6. scx_cgroup_move_task() on it cgrp_moving_from NULL -> WARN The mismatch is that scx_cgroup_can_attach() keys on cgroup identity while migration drives the move on css identity, so a NULL cgrp_moving_from here is a legitimate css-only migration, not a missing prep. The call is already gated on cgrp_moving_from, so just drop the warning. ops.cgroup_prep_move() and ops.cgroup_move() stay paired. Fixes: 819513666966 ("sched_ext: Add cgroup support") Cc: stable@vger.kernel.org # v6.12+ Reported-by: Matt Fleming Closes: https://lore.kernel.org/all/20260601124156.2205704-1-mfleming@cloudflare.com/ Signed-off-by: Tejun Heo Reviewed-by: Andrea Righi diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index c1762420cc35..8e88a25bc602 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -4402,11 +4402,13 @@ void scx_cgroup_move_task(struct task_struct *p) return; /* - * @p must have ops.cgroup_prep_move() called on it and thus - * cgrp_moving_from set. + * scx_cgroup_can_attach() sets cgrp_moving_from only when the task's + * cgroup changes. Migration keys off css rather than cgroup identity, + * so it can hand an unchanged-cgroup task here with cgrp_moving_from + * NULL. Nothing to report to the BPF scheduler then, so skip it and + * keep prep_move and move paired. */ - if (SCX_HAS_OP(sch, cgroup_move) && - !WARN_ON_ONCE(!p->scx.cgrp_moving_from)) + if (SCX_HAS_OP(sch, cgroup_move) && p->scx.cgrp_moving_from) SCX_CALL_OP_TASK(sch, cgroup_move, task_rq(p), p, p->scx.cgrp_moving_from, tg_cgrp(task_group(p)));