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=-3.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, 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 EAD6AC43387 for ; Fri, 18 Jan 2019 07:20:43 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id BA60220855 for ; Fri, 18 Jan 2019 07:20:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="nbyQ9BBf" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BA60220855 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-riscv-bounces+infradead-linux-riscv=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=I7h7zO3/7cL4r5CzozUJdbCuks6i6vJ3+qC75KrODs0=; b=nbyQ9BBfpd+I7i E+EouoVbK2RwasWTpHK48Q/ZomdPWL0SwbvzMY4HCbEQUu6HdSuYNFchMQk3ps7qxzj270wJiZUz3 5KAEgJOt8OAosUcbyZ7jQhujuPxNJ8Jimm8k0RuBBd3kA4aOfnOASJqMsA6G4I2NysLdNWUHqIFCf XVijoaSFjctzVInW2BD0b2QRC6aV33eEKnXNDZpexyjWz10eFA/cPTOsZon9dMDxw9FaOG7/jUDkx yt3YmkiCCilAJQpW6s3SbQ7g2PNf76AlP7aMrzXeSKwTWIqUJylSdxKAz5qy01ITIrRuBKO2aMmIM kvDlapacAiSb4VjVXuGQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gkOSI-0003Mx-BX; Fri, 18 Jan 2019 07:20:42 +0000 Received: from hch by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1gkOSF-0003Lt-1t; Fri, 18 Jan 2019 07:20:39 +0000 Date: Thu, 17 Jan 2019 23:20:38 -0800 From: Christoph Hellwig To: Atish Patra Subject: Re: [PATCH v2 1/8] RISC-V: Do not wait indefinitely in __cpu_up Message-ID: <20190118072038.GA5171@infradead.org> References: <1546940318-9752-1-git-send-email-atish.patra@wdc.com> <1546940318-9752-2-git-send-email-atish.patra@wdc.com> <20190115135125.GA28946@infradead.org> <1995e941-a8cf-c12e-71ae-7b50cf6c0ca5@wdc.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1995e941-a8cf-c12e-71ae-7b50cf6c0ca5@wdc.com> User-Agent: Mutt/1.9.2 (2017-12-15) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Patrick =?iso-8859-1?Q?St=E4hlin?= , Albert Ou , Jason Cooper , Alan Kao , Dmitriy Cherkasov , Anup Patel , Daniel Lezcano , "linux-kernel@vger.kernel.org" , Michael Clark , Christoph Hellwig , Marc Zyngier , Palmer Dabbelt , Andreas Schwab , "linux-riscv@lists.infradead.org" , Thomas Gleixner , Zong Li Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+infradead-linux-riscv=archiver.kernel.org@lists.infradead.org On Thu, Jan 17, 2019 at 06:35:39PM -0800, Atish Patra wrote: > On 1/15/19 5:51 AM, Christoph Hellwig wrote: > > > void *__cpu_up_stack_pointer[NR_CPUS]; > > > void *__cpu_up_task_pointer[NR_CPUS]; > > > +static DECLARE_COMPLETION(cpu_running); > > > void __init smp_prepare_boot_cpu(void) > > > { > > > @@ -81,6 +82,7 @@ void __init setup_smp(void) > > > int __cpu_up(unsigned int cpu, struct task_struct *tidle) > > > { > > > + int ret = 0; > > > int hartid = cpuid_to_hartid_map(cpu); > > > tidle->thread_info.cpu = cpu; > > > @@ -96,10 +98,15 @@ int __cpu_up(unsigned int cpu, struct task_struct *tidle) > > > task_stack_page(tidle) + THREAD_SIZE); > > > WRITE_ONCE(__cpu_up_task_pointer[hartid], tidle); > > > - while (!cpu_online(cpu)) > > > - cpu_relax(); > > > + wait_for_completion_timeout(&cpu_running, > > > + msecs_to_jiffies(1000)); > > > > Having a global completion here worries me. I bet we have some higher > > level serialization, but can we comment or even better lockdep assert on > > that? > > > > Yes. It is serialized from smp.c in smp_init(). It brings one cpu online > at a time for preset_cpu mask. > > Do we still need a lockdep assert ? I guess the real lock is through cpu_hotplug_lock. And yes, a comment or even better lockdep assert would be good. _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv