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 X-Spam-Level: X-Spam-Status: No, score=-20.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 C0465C07E96 for ; Tue, 6 Jul 2021 11:50:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A661762067 for ; Tue, 6 Jul 2021 11:50:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235030AbhGFLxK (ORCPT ); Tue, 6 Jul 2021 07:53:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:47606 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237460AbhGFLgL (ORCPT ); Tue, 6 Jul 2021 07:36:11 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id C5B6B61F14; Tue, 6 Jul 2021 11:28:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1625570883; bh=qsIHHwD5PwQiuhnjDssTRMjsBvM7qqNQlrYb/pmkRdI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NPTW818Dr5LYjXG05lSHZzKpF2By/ikB9d9NPZbggSneie3L5qlzs9cyqgOffbgRg 7L5un1yFIJpYBP1AKsaFm9rwpL3Atzn43NVtonwcml9KJv2MlC9NacRcQQR7RUMB1w J/eaZdGPWZIUBayLwJZvKCMIBvf6DvBFVkWB/LPX81mVUATU3gWQ/x1MPMjos1xaL9 S+m5IbnaSr0JitrAw7T27KgSEVQ9dCp7GSOqG6/KMFVYLJlEmVvlz9z5+bd5jW97f2 nFGMybAV8jIEnuDQmpzJr+gVKkkd3iojQmbnAJGLNbjDyYijHxo94+7A/tg8wAnsD/ TZZaFjqL37xMA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Sebastian Andrzej Siewior , Juri Lelli , Thomas Gleixner , "David S . Miller" , Sasha Levin , netdev@vger.kernel.org Subject: [PATCH AUTOSEL 4.14 10/45] net: Treat __napi_schedule_irqoff() as __napi_schedule() on PREEMPT_RT Date: Tue, 6 Jul 2021 07:27:14 -0400 Message-Id: <20210706112749.2065541-10-sashal@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210706112749.2065541-1-sashal@kernel.org> References: <20210706112749.2065541-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Sebastian Andrzej Siewior [ Upstream commit 8380c81d5c4fced6f4397795a5ae65758272bbfd ] __napi_schedule_irqoff() is an optimized version of __napi_schedule() which can be used where it is known that interrupts are disabled, e.g. in interrupt-handlers, spin_lock_irq() sections or hrtimer callbacks. On PREEMPT_RT enabled kernels this assumptions is not true. Force- threaded interrupt handlers and spinlocks are not disabling interrupts and the NAPI hrtimer callback is forced into softirq context which runs with interrupts enabled as well. Chasing all usage sites of __napi_schedule_irqoff() is a whack-a-mole game so make __napi_schedule_irqoff() invoke __napi_schedule() for PREEMPT_RT kernels. The callers of ____napi_schedule() in the networking core have been audited and are correct on PREEMPT_RT kernels as well. Reported-by: Juri Lelli Signed-off-by: Sebastian Andrzej Siewior Reviewed-by: Thomas Gleixner Reviewed-by: Juri Lelli Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/core/dev.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/net/core/dev.c b/net/core/dev.c index 7ee89125cd53..aa419f3162b8 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -5277,11 +5277,18 @@ EXPORT_SYMBOL(napi_schedule_prep); * __napi_schedule_irqoff - schedule for receive * @n: entry to schedule * - * Variant of __napi_schedule() assuming hard irqs are masked + * Variant of __napi_schedule() assuming hard irqs are masked. + * + * On PREEMPT_RT enabled kernels this maps to __napi_schedule() + * because the interrupt disabled assumption might not be true + * due to force-threaded interrupts and spinlock substitution. */ void __napi_schedule_irqoff(struct napi_struct *n) { - ____napi_schedule(this_cpu_ptr(&softnet_data), n); + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + ____napi_schedule(this_cpu_ptr(&softnet_data), n); + else + __napi_schedule(n); } EXPORT_SYMBOL(__napi_schedule_irqoff); -- 2.30.2