From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 69AD83FD14E; Fri, 24 Apr 2026 20:44:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777063463; cv=none; b=fpu6bvtzbwkKle371r/Mnidh/DjuBKhNBZrSHp5qoRIUDfHXrPomSYMM0Mk4p03C7ZGXTx4vEwGk4hOAM6OkHTSbtBpkoOVCLbqZlZBKlav6amy7NKAzGP/PXNO6XB46lc8tcs92lNYurzq6N6ZprXhqqu72vqaloD+QMNefvr4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777063463; c=relaxed/simple; bh=BqAdOCk1D5oAloLZseRfFomUyN6bCfzFNQZ2SgsjhEc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=cSGpBEQhuyDanj+fG4p+D8u1B9i4BygP360lxwUvE0Nq7ngjYaUVtVxZcOcxs5v2FvUcwrPlESaurxX0rMk31yMQSyN9MseD2PksuAzQykp+8bn0r4Bcrkb56fa7WqijUc/A04aS3wEBEBVA3f8BD2ipQAxJeD4qnIN2xkVzZc8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ewKkUAf3; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ewKkUAf3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EF824C19425; Fri, 24 Apr 2026 20:44:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777063463; bh=BqAdOCk1D5oAloLZseRfFomUyN6bCfzFNQZ2SgsjhEc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ewKkUAf3IHrJNAL27VGyLyuWXOcrND32jt49Lcg1Z1QC/uDBnVYyHBUlgMX+TKVkY wwID+LFuVdAzWMWv7RqDkz/57oaZ/EaDWK6Ktwj8lV13nHlOcX8JLalbfh//GIV/W6 +QI7CDjzo4fDLWpWvYVNUPpUsfDv34MkDobmA4gBPj4GTdGzlVEH0O7mtPcUsSjBym EMLB0ihNEb/DvtfmHXdCzoWau/fAPW5kVDbysafpZ9uM6SJ8tJkerJqVCqTvpZWW2A RFQXZUkoZQH8qOYJWA06llkypxmSm2fmepCUodHVnJhbctVZsrCj7ZNrdOdb4wUnO3 XP1op+NqjGsBg== From: Tejun Heo To: David Vernet , Andrea Righi , Changwoo Min Cc: sched-ext@lists.linux.dev, linux-kernel@vger.kernel.org, Emil Tsalapatis , Chris Mason , Ryan Newton , Tejun Heo , stable@vger.kernel.org Subject: [PATCH 03/13] sched_ext: Skip tasks with stale task_rq in bypass_lb_cpu() Date: Fri, 24 Apr 2026 10:44:08 -1000 Message-ID: <20260424204418.3809733-4-tj@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260424204418.3809733-1-tj@kernel.org> References: <20260424204418.3809733-1-tj@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit bypass_lb_cpu() transfers tasks between per-CPU bypass DSQs without migrating them - task_cpu() only updates when the donee later consumes the task via move_remote_task_to_local_dsq(). If the LB timer fires again before consumption and the new DSQ becomes a donor, @p is still on the previous CPU and task_rq(@p) != donor_rq. @p can't be moved without its own rq locked. Skip such tasks. Fixes: 95d1df610cdc ("sched_ext: Implement load balancer for bypass mode") Cc: stable@vger.kernel.org # v6.19+ Reported-by: Chris Mason Signed-off-by: Tejun Heo --- kernel/sched/ext.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index 89170a0e5779..62b4139a4cc8 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -5002,6 +5002,15 @@ static u32 bypass_lb_cpu(struct scx_sched *sch, s32 donor, if (cpumask_empty(donee_mask)) break; + /* + * If an earlier pass placed @p on @donor_dsq from a different + * CPU and the donee hasn't consumed it yet, @p is still on the + * previous CPU and task_rq(@p) != @donor_rq. @p can't be moved + * without its rq locked. Skip. + */ + if (task_rq(p) != donor_rq) + continue; + donee = cpumask_any_and_distribute(donee_mask, p->cpus_ptr); if (donee >= nr_cpu_ids) continue; -- 2.53.0