From patchwork Fri May 14 10:17:19 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Gleixner X-Patchwork-Id: 439793 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2FDC6C433B4 for ; Fri, 14 May 2021 10:17:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0B06F613E6 for ; Fri, 14 May 2021 10:17:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232983AbhENKSe (ORCPT ); Fri, 14 May 2021 06:18:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52060 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231245AbhENKSd (ORCPT ); Fri, 14 May 2021 06:18:33 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C9560C061574; Fri, 14 May 2021 03:17:21 -0700 (PDT) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1620987439; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type; bh=aQbFo382l0WrRlPyWw81sTdqka757jvjmjuI2q0Ks0I=; b=LwlwSkqROFUWR2q9nIvclJ+JswaCBlsoPhjpSBEhXDR8vhvwAVhP/x2GhaNbs9eFcII97Y j2rCg+EozxT9pt9ftWm8H6wY/KLP0f+fVS0DvVK9xGx7UaJnO8+suqYi96mLWTdYg1fCf3 CiwHQr7x4Bt0eDcFYiCdAXnA/ytRn76L11V+1nvnxqb/D1mN6LiNSXmZYKc/j+8vkUQeZ5 5Raz8yL+U2kr6BAfTw9BzvW6K++O3rIlYlD+bZ7RLah4yCxtj8rY4LmwQiGpWAF3G04rTb c/J2iV8kqJZ7iM0C9S8tTO/lzC/FZP/HnzvhHFPcljIlIEPdZl8Jjmm85GLuKw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1620987439; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type; bh=aQbFo382l0WrRlPyWw81sTdqka757jvjmjuI2q0Ks0I=; b=kMEsLymXP6YQQvNyPfbQaf+rIIfZiyuHz7JtKOB8AzcMe1fxsvvb8e/QSHv3DsWRRx+0z9 NB/ulEp2c7aKIzCA== To: linux-usb@vger.kernel.org, netdev@vger.kernel.org Cc: Michal Svec , "David S. Miller" , Jakub Kicinski , Hayes Wang , Thierry Reding , Lee Jones , Borislav Petkov Subject: [PATCH RFC] r8152: Ensure that napi_schedule() is handled Date: Fri, 14 May 2021 12:17:19 +0200 Message-ID: <877dk162mo.ffs@nanos.tec.linutronix.de> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Thomas Gleixner Date: Fri, 14 May 2021 11:46:08 +0200 The driver invokes napi_schedule() in several places from task context. napi_schedule() raises the NET_RX softirq bit and relies on the calling context to ensure that the softirq is handled. That's usually on return from interrupt or on the outermost local_bh_enable(). But that's not the case here which causes the soft interrupt handling to be delayed to the next interrupt or local_bh_enable(). If the task in which context this is invoked is the last runnable task on a CPU and the CPU goes idle before an interrupt arrives or a local_bh_disable/enable() pair handles the pending soft interrupt then the NOHZ idle code emits the following warning. NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!! Prevent this by wrapping the napi_schedule() invocation from task context into a local_bh_disable/enable() pair. Reported-by: Michal Svec Signed-off-by: Thomas Gleixner --- Note: That's not the first incident of this. Shouldn't napi_schedule() have a debug check (under lockdep) to catch this? --- drivers/net/usb/r8152.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) --- a/drivers/net/usb/r8152.c +++ b/drivers/net/usb/r8152.c @@ -1543,6 +1543,17 @@ void write_mii_word(struct net_device *n r8152_mdio_write(tp, reg, val); } +/* + * Wrapper around napi_schedule() to ensure that the raised network softirq + * is actually handled. + */ +static void r8152_napi_schedule(struct napi_struct *napi) +{ + local_bh_disable(); + napi_schedule(napi); + local_bh_enable(); +} + static int r8152_submit_rx(struct r8152 *tp, struct rx_agg *agg, gfp_t mem_flags); @@ -1753,7 +1764,7 @@ static void read_bulk_callback(struct ur spin_lock_irqsave(&tp->rx_lock, flags); list_add_tail(&agg->list, &tp->rx_done); spin_unlock_irqrestore(&tp->rx_lock, flags); - napi_schedule(&tp->napi); + r8152_napi_schedule(&tp->napi); return; case -ESHUTDOWN: rtl_set_unplug(tp); @@ -2640,7 +2651,7 @@ int r8152_submit_rx(struct r8152 *tp, st netif_err(tp, rx_err, tp->netdev, "Couldn't submit rx[%p], ret = %d\n", agg, ret); - napi_schedule(&tp->napi); + r8152_napi_schedule(&tp->napi); } return ret; @@ -8202,7 +8213,7 @@ static int rtl8152_post_reset(struct usb usb_submit_urb(tp->intr_urb, GFP_KERNEL); if (!list_empty(&tp->rx_done)) - napi_schedule(&tp->napi); + r8152_napi_schedule(&tp->napi); return 0; } @@ -8256,7 +8267,7 @@ static int rtl8152_runtime_resume(struct smp_mb__after_atomic(); if (!list_empty(&tp->rx_done)) - napi_schedule(&tp->napi); + r8152_napi_schedule(&tp->napi); usb_submit_urb(tp->intr_urb, GFP_NOIO); } else {