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=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 6F8C8C63798 for ; Mon, 23 Nov 2020 23:58:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 077C720724 for ; Mon, 23 Nov 2020 23:58:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="CFRCTaZA" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728025AbgKWX6G (ORCPT ); Mon, 23 Nov 2020 18:58:06 -0500 Received: from mail.kernel.org ([198.145.29.99]:35354 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727931AbgKWX6F (ORCPT ); Mon, 23 Nov 2020 18:58:05 -0500 Received: from localhost (unknown [176.167.152.233]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2051A20724; Mon, 23 Nov 2020 23:58:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1606175884; bh=wlBAJHyNfRR9V9uKfIpJvzXL6dugQ5jSJ9PZbyQVK0w=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=CFRCTaZAgmKkRgWK4QqyETUgI+4tgN0UAq7RB9jbFcwi4RliJmfWhNnxQAcigLBCR FN+MYO/tZhuK0KF5bqdJPRF4oO31elR3z/Li3TGW9+/te1VGJES/iAEXj/tvELbdcb lf9dhGlX6/nYJJ5+rLwfRWNydnK9WXypNmscWo1g= Date: Tue, 24 Nov 2020 00:58:01 +0100 From: Frederic Weisbecker To: Thomas Gleixner Cc: LKML , Peter Zijlstra , Paul McKenney , Sebastian Andrzej Siewior , Arnd Bergmann , "James E.J. Bottomley" , Helge Deller , linux-parisc@vger.kernel.org, Yoshinori Sato , Rich Felker , linux-sh@vger.kernel.org, Jeff Dike , Richard Weinberger , Anton Ivanov , linux-um@lists.infradead.org, Russell King , Marc Zyngier , Valentin Schneider , linux-arm-kernel@lists.infradead.org, Catalin Marinas , Will Deacon Subject: Re: [patch 14/19] softirq: Make softirq control and processing RT aware Message-ID: <20201123235801.GE1751@lothringen> References: <20201113140207.499353218@linutronix.de> <20201113141734.324061522@linutronix.de> <20201123134437.GA95787@lothringen> <87r1ojnaai.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87r1ojnaai.fsf@nanos.tec.linutronix.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 23, 2020 at 08:27:33PM +0100, Thomas Gleixner wrote: > On Mon, Nov 23 2020 at 14:44, Frederic Weisbecker wrote: > > On Fri, Nov 13, 2020 at 03:02:21PM +0100, Thomas Gleixner wrote: > >> + /* > >> + * Adjust softirq count to SOFTIRQ_OFFSET which makes > >> + * in_serving_softirq() become true. > >> + */ > >> + cnt = SOFTIRQ_OFFSET; > >> + __local_bh_enable(cnt, false); > > > > But then you enter __do_softirq() with softirq_count() == SOFTIRQ_OFFSET. > > __do_softirq() calls softirq_handle_begin() which then sets it back to > > SOFTIRQ_DISABLE_OFFSET... > > The RT variant of it added in this very same patch > > +static inline void softirq_handle_begin(void) { } > > +static inline void softirq_handle_end(void) { } Ah but then account_irq_enter_time() is called with SOFTIRQ_OFFSET (it's currently called with softirq_count == 0 at this point) and that may mess up irqtime accounting which relies on it. It could spuriously account all the time between the last (soft-)IRQ exit until now as softirq time.