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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 D6578C636C9 for ; Thu, 15 Jul 2021 18:50:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C201E613E5 for ; Thu, 15 Jul 2021 18:50:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240334AbhGOSxb (ORCPT ); Thu, 15 Jul 2021 14:53:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:51408 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240014AbhGOSsz (ORCPT ); Thu, 15 Jul 2021 14:48:55 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id D6F8D613D3; Thu, 15 Jul 2021 18:46:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626374761; bh=YfO+ILk/xfSGs3uV8mw0YqMe/28CtrVO21a5gF/WaOo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=camrIT80Db9p5vmLxk2jQAdKwyV2bIM/6GzQBbB7B2Au1+a6icDa8oF6PPJNcYMp4 AgAoqmQs5pbomj/3JskBUYhjB973ojF6ty0FolEa40jmRGv5rVwKDT1qvrCrC8v09T iQ3ExcOJiZCnXzQvGjGEVyXlgFPaStFREuejikW0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Juri Lelli , Sebastian Andrzej Siewior , Thomas Gleixner , "David S. Miller" , Sasha Levin Subject: [PATCH 5.10 015/215] net: Treat __napi_schedule_irqoff() as __napi_schedule() on PREEMPT_RT Date: Thu, 15 Jul 2021 20:36:27 +0200 Message-Id: <20210715182601.404788917@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210715182558.381078833@linuxfoundation.org> References: <20210715182558.381078833@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 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 0c9ce36afc8c..2fdf30eefc59 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -6433,11 +6433,18 @@ 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