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 86A97C77B7C for ; Sun, 28 May 2023 19:33:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230293AbjE1TdE (ORCPT ); Sun, 28 May 2023 15:33:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49554 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230298AbjE1TdC (ORCPT ); Sun, 28 May 2023 15:33:02 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 89709C7 for ; Sun, 28 May 2023 12:33:01 -0700 (PDT) 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 1D5CB61DC5 for ; Sun, 28 May 2023 19:33:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 16367C433D2; Sun, 28 May 2023 19:32:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1685302380; bh=p/1qBNSjHhVQDzfbR+YBDXcVD80c/BNa3Oh5NZ0Pr2s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=x+/YBcLerDOITx/8OksF9OFNxiE6bSvrbrqSvCguMcqe5LD1oW9+1DGBFe77P2euZ 4Fd6aZS16tCXPhWxPvXzcgSTkqpo1ZGZauhfkxKVvZGyI3XEuJN9dxYLZrSczvn4ZK dexUiUWqNmAJBNOiankEe/WvQ3EgwDr1KA3HgkOg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Tariq Toukan , Jakub Kicinski , Simon Horman , "David S. Miller" Subject: [PATCH 6.3 111/127] net/mlx5e: do as little as possible in napi poll when budget is 0 Date: Sun, 28 May 2023 20:11:27 +0100 Message-Id: <20230528190839.871037946@linuxfoundation.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230528190836.161231414@linuxfoundation.org> References: <20230528190836.161231414@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Jakub Kicinski commit afbed3f74830163f9559579dee382cac3cff82da upstream. NAPI gets called with budget of 0 from netpoll, which has interrupts disabled. We should try to free some space on Tx rings and nothing else. Specifically do not try to handle XDP TX or try to refill Rx buffers - we can't use the page pool from IRQ context. Don't check if IRQs moved, either, that makes no sense in netpoll. Netpoll calls _all_ the rings from whatever CPU it happens to be invoked on. In general do as little as possible, the work quickly adds up when there's tens of rings to poll. The immediate stack trace I was seeing is: __do_softirq+0xd1/0x2c0 __local_bh_enable_ip+0xc7/0x120 page_pool_put_defragged_page+0x267/0x320 mlx5e_free_xdpsq_desc+0x99/0xd0 mlx5e_poll_xdpsq_cq+0x138/0x3b0 mlx5e_napi_poll+0xc3/0x8b0 netpoll_poll_dev+0xce/0x150 AFAIU page pool takes a BH lock, releases it and since BH is now enabled tries to run softirqs. Reviewed-by: Tariq Toukan Fixes: 60bbf7eeef10 ("mlx5: use page_pool for xdp_return_frame call") Signed-off-by: Jakub Kicinski Reviewed-by: Simon Horman Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- drivers/net/ethernet/mellanox/mlx5/core/en_txrx.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) --- a/drivers/net/ethernet/mellanox/mlx5/core/en_txrx.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_txrx.c @@ -161,20 +161,22 @@ int mlx5e_napi_poll(struct napi_struct * } } + /* budget=0 means we may be in IRQ context, do as little as possible */ + if (unlikely(!budget)) + goto out; + busy |= mlx5e_poll_xdpsq_cq(&c->xdpsq.cq); if (c->xdp) busy |= mlx5e_poll_xdpsq_cq(&c->rq_xdpsq.cq); - if (likely(budget)) { /* budget=0 means: don't poll rx rings */ - if (xsk_open) - work_done = mlx5e_poll_rx_cq(&xskrq->cq, budget); + if (xsk_open) + work_done = mlx5e_poll_rx_cq(&xskrq->cq, budget); - if (likely(budget - work_done)) - work_done += mlx5e_poll_rx_cq(&rq->cq, budget - work_done); + if (likely(budget - work_done)) + work_done += mlx5e_poll_rx_cq(&rq->cq, budget - work_done); - busy |= work_done == budget; - } + busy |= work_done == budget; mlx5e_poll_ico_cq(&c->icosq.cq); if (mlx5e_poll_ico_cq(&c->async_icosq.cq))