From nobody Sun Feb 8 05:43:09 2026 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 8C329326D70 for ; Tue, 13 Jan 2026 08:52:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768294368; cv=none; b=mT45+uqOjECkRlWu5Uz3qqnri/VbZBlwTlK/KLBQigHO6UJWi+5mxWu/ApSaj2DHWUVYWgoviXYwQH7gHNie//NVDfve0DPFO70KXQCwz6NcFoiYM09sr546Kpa0kBKCS/irPvNWaHx2E0pjtnWjn30zOWHPrx3qY4kdQbA2pYw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768294368; c=relaxed/simple; bh=EYdKYp9uNIQTwsOPbKx2jcNn4sl8MGsNsGdrtdExWfc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=q/5iOHVINtda/+JVCsO+SZcXAGWwoOjY20KX2ltCaLc07m+WDg2SgkGM4zFx6/v1XyG685mDFShqNQXiSmShAG4n6iG49ovUZsX4dIm8VMmXHt8DT9U6/QH1uiFA1sUQcY7w3jxSPhHPLZno7SXbqP5F7ULH5Z5kZ8BosHyzw1o= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=Lltl/4c6; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Lltl/4c6" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1768294366; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=FYhhDcqCr9P9dKeHh97dERntGS6xdlCNaNvqD9Igi9M=; b=Lltl/4c6Blp4H5bgMRgm7H8LvrE7m4hNzk5NMjUz42ScJYnnaoZXM/5vaTPc78lHo0RVhb ++wsLES4CFzporrRNTC4o7M9fzYSjakrS+t+xbT3WdPQ6jefXAUY8AxZsx6QkeT7+ZDmsr uS9qXtsoXK/1XeHQXpYp304+i6Yg2Xs= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-211-Z2Vp5LFvMk6CAUrKXEFCcA-1; Tue, 13 Jan 2026 03:52:43 -0500 X-MC-Unique: Z2Vp5LFvMk6CAUrKXEFCcA-1 X-Mimecast-MFC-AGG-ID: Z2Vp5LFvMk6CAUrKXEFCcA_1768294362 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 10F9D19560AA; Tue, 13 Jan 2026 08:52:42 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.csb (unknown [10.45.224.43]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 0305A180066A; Tue, 13 Jan 2026 08:52:38 +0000 (UTC) From: Gabriele Monaco To: juri.lelli@redhat.com, peterz@infradead.org, Ingo Molnar , linux-kernel@vger.kernel.org Cc: williams@redhat.com, Gabriele Monaco Subject: [PATCH] sched/deadline: Fix server stopping with runnable tasks Date: Tue, 13 Jan 2026 09:52:01 +0100 Message-ID: <20260113085159.114226-3-gmonaco@redhat.com> In-Reply-To: References: 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-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Content-Type: text/plain; charset="utf-8" The deadline server can currently stop due to idle although fair tasks are runnable. This happens essentially when: * the server is set to idle, a task wakes up, the server stops * a task wakes up, the server sets itself to idle and stops right away Address both cases by clearing the server idle flag whenever a fair task wakes up and accounting also for pending tasks in the definition of idle. Signed-off-by: Gabriele Monaco --- This is really quick and dirty but seems to fix it according to the models. I also updated the chart to show what is happening here. I added the same event (server_resume) to the model. kernel/sched/deadline.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 138136742871..1070e93350df 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1376,7 +1376,7 @@ update_stats_dequeue_dl(struct dl_rq *dl_rq, struct s= ched_dl_entity *dl_se, int =20 static void update_curr_dl_se(struct rq *rq, struct sched_dl_entity *dl_se= , s64 delta_exec) { - bool idle =3D rq->curr =3D=3D rq->idle; + bool idle =3D rq->curr =3D=3D rq->idle && !rq->nr_running && !rq->ttwu_pe= nding; s64 scaled_delta_exec; =20 if (unlikely(delta_exec <=3D 0)) { @@ -1560,8 +1560,8 @@ void dl_server_update(struct sched_dl_entity *dl_se, = s64 delta_exec) * | 8 | B:zero_laxity-wait | | | * | | | <---+ | * | +--------------------------------+ | - * | | ^ ^ 2 | - * | | 7 | 2 +--------------------+ + * | | ^ ^ 2 | + * | | 7 | 2, 1 +----------------+ * | v | * | +-------------+ | * +-- | C:idle-wait | -+ @@ -1606,8 +1606,11 @@ void dl_server_update(struct sched_dl_entity *dl_se,= s64 delta_exec) * dl_defer_idle =3D 0 * * - * [1] A->B, A->D + * [1] A->B, A->D, C->B * dl_server_start() + * dl_defer_idle =3D 0; + * if (dl_server_active) + * return; // [B] * dl_server_active =3D 1; * enqueue_dl_entity() * update_dl_entity(WAKEUP) @@ -1741,6 +1744,7 @@ void dl_server_start(struct sched_dl_entity *dl_se) { struct rq *rq =3D dl_se->rq; =20 + dl_se->dl_defer_idle =3D 0; if (!dl_server(dl_se) || dl_se->dl_server_active) return; =20 base-commit: 0f61b1860cc3f52aef9036d7235ed1f017632193 --=20 2.52.0