From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CD9CAC4332F for ; Tue, 15 Feb 2022 06:33:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234509AbiBOGdF (ORCPT ); Tue, 15 Feb 2022 01:33:05 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:44540 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234457AbiBOGct (ORCPT ); Tue, 15 Feb 2022 01:32:49 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 72EA4B1506 for ; Mon, 14 Feb 2022 22:32:40 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 0DC7A61522 for ; Tue, 15 Feb 2022 06:32:40 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 85673C340F1; Tue, 15 Feb 2022 06:32:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1644906759; bh=Zg83C8t7rW3yK3qRsHoq1tnBJ2Z9zK2+F9DGpEszxp4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JHFx9xx7MBI0d8vbVMzEcr85MBdsBNRa6L1oI1DHtvSBxu1v8Mr0H74kHZN5tDkqf m4iAKs2mPqg0dldixOXpZHcXOsuPQD3ALrpfZfguxDD9MJoOH3Tyk7/plYZwV0ePBS 84FCF8rTZHycQcRStJPY9GwZY4DRlODceiebqTIuKNxQ/couu9jbZnxfsnSiag6ybs TSP7i4hO0ZZ5mqmnFk0zMwd4GHxbxeUeQUTgK63IX/0ujQ/xdLgWxpZ864XjN5EF5N 7Eijfm5napQumuuSsZqJwC3Xo1sDlejpH3qmUBNG6IdSBchXTW+EShv/+Gcso8pClu 6rAKy8qo9ATQQ== From: Saeed Mahameed To: "David S. Miller" , Jakub Kicinski Cc: netdev@vger.kernel.org, Tariq Toukan , Maxim Mikityanskiy , Saeed Mahameed Subject: [net-next 07/15] net/mlx5e: Sync txq2sq updates with mlx5e_xmit for HTB queues Date: Mon, 14 Feb 2022 22:32:21 -0800 Message-Id: <20220215063229.737960-8-saeed@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220215063229.737960-1-saeed@kernel.org> References: <20220215063229.737960-1-saeed@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Maxim Mikityanskiy This commit makes necessary changes to guarantee that txq2sq remains stable while mlx5e_xmit is running. Proper synchronization is added for HTB TX queues. All updates to txq2sq are performed while the corresponding queue is disabled (i.e. mlx5e_xmit doesn't run on that queue). smp_wmb after each change guarantees that mlx5e_xmit can see the updated value after the queue is enabled. Comments explaining this mechanism are added to mlx5e_xmit. When an HTB SQ can be deleted (after deleting an HTB node), synchronize with RCU to wait for mlx5e_select_queue to finish and stop selecting that queue, before we re-enable it to avoid TX timeout watchdog alarms. Signed-off-by: Maxim Mikityanskiy Reviewed-by: Tariq Toukan Signed-off-by: Saeed Mahameed --- .../net/ethernet/mellanox/mlx5/core/en/qos.c | 24 +++++++++++++++---- .../net/ethernet/mellanox/mlx5/core/en_tx.c | 13 ++++++++++ 2 files changed, 33 insertions(+), 4 deletions(-) diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c b/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c index c1e07496c89c..ff45840581e3 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c @@ -50,7 +50,6 @@ static int mlx5e_find_unused_qos_qid(struct mlx5e_priv *priv) struct mlx5e_qos_node { struct hlist_node hnode; - struct rcu_head rcu; struct mlx5e_qos_node *parent; u64 rate; u32 bw_share; @@ -132,7 +131,11 @@ static void mlx5e_sw_node_delete(struct mlx5e_priv *priv, struct mlx5e_qos_node __clear_bit(node->qid, priv->htb.qos_used_qids); mlx5e_update_tx_netdev_queues(priv); } - kfree_rcu(node, rcu); + /* Make sure this qid is no longer selected by mlx5e_select_queue, so + * that mlx5e_reactivate_qos_sq can safely restart the netdev TX queue. + */ + synchronize_net(); + kfree(node); } /* TX datapath API */ @@ -273,10 +276,18 @@ static int mlx5e_open_qos_sq(struct mlx5e_priv *priv, struct mlx5e_channels *chs static void mlx5e_activate_qos_sq(struct mlx5e_priv *priv, struct mlx5e_qos_node *node) { struct mlx5e_txqsq *sq; + u16 qid; sq = mlx5e_get_qos_sq(priv, node->qid); - WRITE_ONCE(priv->txq2sq[mlx5e_qid_from_qos(&priv->channels, node->qid)], sq); + qid = mlx5e_qid_from_qos(&priv->channels, node->qid); + + /* If it's a new queue, it will be marked as started at this point. + * Stop it before updating txq2sq. + */ + mlx5e_tx_disable_queue(netdev_get_tx_queue(priv->netdev, qid)); + + priv->txq2sq[qid] = sq; /* Make the change to txq2sq visible before the queue is started. * As mlx5e_xmit runs under a spinlock, there is an implicit ACQUIRE, @@ -299,8 +310,13 @@ static void mlx5e_deactivate_qos_sq(struct mlx5e_priv *priv, u16 qid) qos_dbg(priv->mdev, "Deactivate QoS SQ qid %u\n", qid); mlx5e_deactivate_txqsq(sq); - /* The queue is disabled, no synchronization with datapath is needed. */ priv->txq2sq[mlx5e_qid_from_qos(&priv->channels, qid)] = NULL; + + /* Make the change to txq2sq visible before the queue is started again. + * As mlx5e_xmit runs under a spinlock, there is an implicit ACQUIRE, + * which pairs with this barrier. + */ + smp_wmb(); } static void mlx5e_close_qos_sq(struct mlx5e_priv *priv, u16 qid) diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c index 9c91ef0e1ed2..726661774979 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c @@ -691,8 +691,21 @@ netdev_tx_t mlx5e_xmit(struct sk_buff *skb, struct net_device *dev) struct mlx5e_txqsq *sq; u16 pi; + /* All changes to txq2sq are performed in sync with mlx5e_xmit, when the + * queue being changed is disabled, and smp_wmb guarantees that the + * changes are visible before mlx5e_xmit tries to read from txq2sq. It + * guarantees that the value of txq2sq[qid] doesn't change while + * mlx5e_xmit is running on queue number qid. smb_wmb is paired with + * HARD_TX_LOCK around ndo_start_xmit, which serves as an ACQUIRE. + */ sq = priv->txq2sq[skb_get_queue_mapping(skb)]; if (unlikely(!sq)) { + /* Two cases when sq can be NULL: + * 1. The HTB node is registered, and mlx5e_select_queue + * selected its queue ID, but the SQ itself is not yet created. + * 2. HTB SQ creation failed. Similar to the previous case, but + * the SQ won't be created. + */ dev_kfree_skb_any(skb); return NETDEV_TX_OK; } -- 2.34.1