From nobody Mon Feb 9 01:21:43 2026 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 1203E155757; Fri, 30 Jan 2026 22:12:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769811125; cv=none; b=CqomRSTDdnCAhZM/4UdapO+QC/bgEH+7l9MATrG0cZYk8GNYtO1jWTaewtb4RoO/BLn7dyzyjVmhfhmGi3KLJ6IWCtyQ6aSCS57tz9IN/zt6ooIA6tb7HWhqPl1GpS967JvesOHIwX5PaUjOizUT/odJ6rZBiXz8wUdGBuvmsVQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769811125; c=relaxed/simple; bh=BvTXWL3Cruj7I4z1VCKd5m4wOfI2PtekiwsGWB6QY5s=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=OKaOF4siMERvsGaqjReVQcLmmNntY9OfVve5ZWvvDoEN/t/FeCzuN3gKycJ8Fsv2s+IzWXcoPCsmdtEIvSky7itby/+pMk/GurCpBW77oTt0XokYeV8EcZvgY7qCZ54adlPF4K+y+Q9QYesfs0Ls3KqZ6hpTNDdcBqAD9PZjg1w= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=boTZRv16; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=xAzgJyZw; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="boTZRv16"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="xAzgJyZw" Date: Fri, 30 Jan 2026 22:12:01 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1769811122; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=b/qPKRGJkrUmxJVT9vEqA3kL3IBbH43f2gsKUbMgdew=; b=boTZRv16gOQ+egaDfaeBhM16R2gJ+boGwMhDubgJMMxHzcvoc68EbxV7l7Eqi1S7EukXIM go8NjAyFMbtgC+fsmKUlXHCCvdffn8S2D0ca3dBg2yNbEyca22A/vV2jgsmr4ExbvGSz8+ 1B5Dwow0he2j9A3NjpHjwQsdHEF/eaQq+HXOpNi6n1Jq5d1PXU6JV04a0ALGkv6gDIugJx YbrKxJqTBO2ZQBKRGV28AhjDooiQUPIcbKzLfa/R/6zGRmSvjtqpoQHgHueZfwQdYEBuvx RONoHQwhbm+4sxXImj1L0s6mdVMOARvoHx66hHIaYnb+KuR9dkQBAvPh0z2ylQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1769811122; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=b/qPKRGJkrUmxJVT9vEqA3kL3IBbH43f2gsKUbMgdew=; b=xAzgJyZwO9nGC9gy1IP7rIe5fPwcXg3hgDcALvLQedfqMPaNHW4/dO68YMlhqR7bWwoxNr T4a2rZyj4iisgVDw== From: "tip-bot2 for Peter Zijlstra" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/urgent] sched/deadline: Fix 'stuck' dl_server Cc: Andrea@tip-bot2.tec.linutronix.de, Righi@tip-bot2.tec.linutronix.de, arighi@nvidia.com, "Peter Zijlstra (Intel)" , Juri Lelli , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20260130124100.GC1079264@noisy.programming.kicks-ass.net> References: <20260130124100.GC1079264@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <176981112143.2495410.4348604834756100373.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Precedence: bulk Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable The following commit has been merged into the sched/urgent branch of tip: Commit-ID: 115135422562e2f791e98a6f55ec57b2da3b3a95 Gitweb: https://git.kernel.org/tip/115135422562e2f791e98a6f55ec57b2d= a3b3a95 Author: Peter Zijlstra AuthorDate: Fri, 30 Jan 2026 13:41:00 +01:00 Committer: Peter Zijlstra CommitterDate: Fri, 30 Jan 2026 23:06:06 +01:00 sched/deadline: Fix 'stuck' dl_server Andrea reported the dl_server getting stuck for him. He tracked it down to a state where dl_server_start() saw dl_defer_running=3D=3D1, but the dl_server's job is no longer valid at the time of dl_server_start(). In the state diagram this corresponds to [4] D->A (or dl_server_stop() due to no more runnable tasks) followed by [1], which in case of a lapsed deadline must then be A->B. Now our A has dl_defer_running=3D=3D1, while B demands dl_defer_running=3D=3D0, therefore it must get cleared when the CBS wakeup rules demand a replenish. Fixes: a110a81c52a9 ("sched/deadline: Deferrable dl server") Reported-by: Andrea Righi arighi@nvidia.com Signed-off-by: Peter Zijlstra (Intel) Acked-by: Juri Lelli Tested-by: Andrea Righi arighi@nvidia.com Link: https://lkml.kernel.org/r/20260123161645.2181752-1-arighi@nvidia.com Link: https://patch.msgid.link/20260130124100.GC1079264@noisy.programming.k= icks-ass.net --- kernel/sched/deadline.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index c509f2e..7bcde71 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1034,6 +1034,12 @@ static void update_dl_entity(struct sched_dl_entity = *dl_se) return; } =20 + /* + * When [4] D->A is followed by [1] A->B, dl_defer_running + * needs to be cleared, otherwise it will fail to properly + * start the zero-laxity timer. + */ + dl_se->dl_defer_running =3D 0; replenish_dl_new_period(dl_se, rq); } else if (dl_server(dl_se) && dl_se->dl_defer) { /* @@ -1655,6 +1661,12 @@ void dl_server_update(struct sched_dl_entity *dl_se,= s64 delta_exec) * dl_server_active =3D 1; * enqueue_dl_entity() * update_dl_entity(WAKEUP) + * if (dl_time_before() || dl_entity_overflow()) + * dl_defer_running =3D 0; + * replenish_dl_new_period(); + * // fwd period + * dl_throttled =3D 1; + * dl_defer_armed =3D 1; * if (!dl_defer_running) * dl_defer_armed =3D 1; * dl_throttled =3D 1;