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=-2.1 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, USER_AGENT_MUTT autolearn=ham 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 F30ACC6778A for ; Thu, 5 Jul 2018 18:05:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AFD6F22438 for ; Thu, 5 Jul 2018 18:05:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="wOsbE/Wo" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AFD6F22438 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753812AbeGESFu (ORCPT ); Thu, 5 Jul 2018 14:05:50 -0400 Received: from merlin.infradead.org ([205.233.59.134]:58330 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753405AbeGESFt (ORCPT ); Thu, 5 Jul 2018 14:05:49 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=LrTvPfC6gZ84+BiplJcgusDzGTOkKRssYS7e2v5kEmM=; b=wOsbE/WomtJXRYwBfLuSFN3It 3RMUUQn3IxY/yRdZcccvSHQpdXGSKSCDx3kEh0nm5Kx4jWn9zzDZw2OpXjwkd3K0LFyyoKf3iW596 edJcxdst8dH0OHB5VKJE/0lSnHm53LiP148iugJ+oAGdCnd8cn5fa2w5jBU0UFRA9uGc41UMVK5a+ K2YQzZo2a5Azns/u+6Ij3RckPV1DWRCfXwa9GyqeeHpc2Exi4foyVbyvzHXIWXE0QYBPNbXwnBGLD xUNOtfVoLnzEgXnQvOstaAzwpYArlwRpQcZOyAEDzVAf190+FaeUcvE7SP8bIAqRU4XxUoq/PTZAi 2Du4KRpsQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fb8cr-0002qM-4X; Thu, 05 Jul 2018 18:05:05 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 733CA20289CF4; Thu, 5 Jul 2018 20:05:03 +0200 (CEST) Date: Thu, 5 Jul 2018 20:05:03 +0200 From: Peter Zijlstra To: Guo Ren Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, daniel.lezcano@linaro.org, jason@lakedaemon.net, arnd@arndb.de, c-sky_gcc_upstream@c-sky.com, gnu-csky@mentor.com, thomas.petazzoni@bootlin.com, wbx@uclibc-ng.org, green.hu@gmail.com Subject: Re: [PATCH V2 16/19] csky: SMP support Message-ID: <20180705180503.GH2530@hirez.programming.kicks-ass.net> References: <21d859826fe19aecaa2aefe3103d6d33e6f1b925.1530465326.git.ren_guo@c-sky.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <21d859826fe19aecaa2aefe3103d6d33e6f1b925.1530465326.git.ren_guo@c-sky.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 02, 2018 at 01:30:19AM +0800, Guo Ren wrote: > +static irqreturn_t handle_ipi(int irq, void *dev) > +{ > + unsigned long *pending_ipis = &ipi_data[smp_processor_id()].bits; > + > + while (true) { > + unsigned long ops; > + > + /* Order bit clearing and data access. */ > + mb(); > + > + ops = xchg(pending_ipis, 0); > + if (ops == 0) > + return IRQ_HANDLED; > + > + if (ops & (1 << IPI_RESCHEDULE)) > + scheduler_ipi(); > + > + if (ops & (1 << IPI_CALL_FUNC)) > + generic_smp_call_function_interrupt(); > + > + BUG_ON((ops >> IPI_MAX) != 0); > + > + /* Order data access and bit testing. */ > + mb(); > + } > + > + return IRQ_HANDLED; > +} > + > +static void (*send_arch_ipi)(const unsigned long *mask, unsigned long irq) = NULL; > + > +void __init set_send_ipi(void (*func)(const unsigned long *, unsigned long)) > +{ > + if (send_arch_ipi) > + return; > + > + send_arch_ipi = func; > +} > + > +static void > +send_ipi_message(const struct cpumask *to_whom, enum ipi_message_type operation) > +{ > + int i; > + > + mb(); > + for_each_cpu(i, to_whom) > + set_bit(operation, &ipi_data[i].bits); > + > + mb(); > + send_arch_ipi(cpumask_bits(to_whom), IPI_IRQ); > +} Please explain those mb()'s... I'm thinking you meant to use smp_mb(). But then for handle_ipi(), the xchg() should already imply all those. And the send_ipi_message() only needs the second.