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 4DE6F2D5436; Tue, 21 Jul 2026 17:58:22 +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=1784656704; cv=none; b=hFovM+Cmtlpa1lJbTMZLs8cF6dWUKV6AmBqFurC8cuQhDKW+zrir3kIg4MLIr0hXtKM1tu1YuKSdyF9xXNeKvavlhdY3znHGUGIZL+IxNNTZ31R6v/wqzwm3BZLzuPlSanmqoTFveDWiT4sBPnQawYAK2HSApTBEh8867up5SCA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784656704; c=relaxed/simple; bh=YwiraYOq9t8mkAhjViXBCu/GhtDg9D1ogpE/gnZ05pw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=oj1OTAIjC6s3MSIX5wOKnG1bsYg2/cJcqRBqLh61RO1hgsx5+lbqRCP8Mr5faajpmjrske3nkqDLMsiW1Trn5jp9OAxhsCRMl+a5IcMmyiL2y3zVR6LmzMyGCEQfr8UvbEK6ZkE/Q4rIgKgXu+RdhE9fcVaUmPFthhjG+ugaRsE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=qkhmmOiP; 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="qkhmmOiP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3FDE41F000E9; Tue, 21 Jul 2026 17:58:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784656702; bh=7c4fvYdoHxkmy89wMt2X/2xK9p/67o/j6X2basRe5y0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=qkhmmOiPRVK8FBPbxs9Lp/pkLgyb1HHbzBnXsKF1ESJeQeFJWQNpkAt+uiMcfj3R8 NkwuVGxaXk6rg9zmIUe6s44sn+dwJC+y/TFHDBD+9lg2RisV318KY3f2QCaOlEAgnu Iq9Ud1RtjCj4wV4LMCEA09MWmOlm9z7/WFJ0OfJ0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Anirudh Gupta , Jamal Hadi Salim , Victor Nogueira , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.18 0487/1611] net/sched: sch_hfsc: Dont make class passive twice Date: Tue, 21 Jul 2026 17:10:03 +0200 Message-ID: <20260721152526.288470434@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152514.750365251@linuxfoundation.org> References: <20260721152514.750365251@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Victor Nogueira [ Upstream commit 90b662ea25f5e83bb3b8ccec5b93ced810b92fb8 ] update_vf() is called from two places for the same class during a single dequeue when the class's child qdisc (e.g. codel/fq_codel) drops its last packets while dequeuing: 1. The child calls qdisc_tree_reduce_backlog(), which, now that the child is empty, invokes hfsc_qlen_notify() -> update_vf(cl, 0, 0) and turns the class passive (cl_nactive is decremented up the hierarchy). 2. hfsc_dequeue() then calls update_vf(cl, qdisc_pkt_len(skb), cur_time) to charge the dequeued bytes. On the second call the class is already passive, but its child qdisc is still empty, so update_vf() arms go_passive again: if (cl->qdisc->q.qlen == 0 && cl->cl_flags & HFSC_FSC) go_passive = 1; The leaf is then skipped by the cl_nactive == 0 check inside the loop, which does not clear go_passive, so the stale go_passive propagates to the parent and decrements its cl_nactive a second time. A parent that still has other active children is driven to cl_nactive == 0 and removed from the vttree, even though those siblings are still backlogged. They are never dequeued again and the qdisc stalls. Fix this by only arming go_passive when the class is actually active, so an already-passive class no longer triggers a second passive transition. The byte accounting (cl->cl_total += len) still runs for every ancestor, so dequeued bytes continue to be counted exactly once. Fixes: 51eb3b65544c ("sch_hfsc: make hfsc_qlen_notify() idempotent") Reported-by: Anirudh Gupta Closes: https://lore.kernel.org/netdev/CAN2cbVe79oj0O9==m4+4x3v+O+qzRagA=2=wkrp9i9=CqYvyZA@mail.gmail.com/ Tested-by: Anirudh Gupta Acked-by: Jamal Hadi Salim Signed-off-by: Victor Nogueira Link: https://patch.msgid.link/20260610132824.3027549-1-victor@mojatatu.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/sched/sch_hfsc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c index 9c6e6d2b47f8e3..601f99dd989aeb 100644 --- a/net/sched/sch_hfsc.c +++ b/net/sched/sch_hfsc.c @@ -753,7 +753,7 @@ update_vf(struct hfsc_class *cl, unsigned int len, u64 cur_time) u64 f; /* , myf_bound, delta; */ int go_passive = 0; - if (cl->qdisc->q.qlen == 0 && cl->cl_flags & HFSC_FSC) + if (cl->qdisc->q.qlen == 0 && cl->cl_flags & HFSC_FSC && cl->cl_nactive) go_passive = 1; for (; cl->cl_parent != NULL; cl = cl->cl_parent) { -- 2.53.0