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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 CE1FFC2BB1D for ; Tue, 17 Mar 2020 10:06:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B0BE020714 for ; Tue, 17 Mar 2020 10:06:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726189AbgCQKGQ (ORCPT ); Tue, 17 Mar 2020 06:06:16 -0400 Received: from foss.arm.com ([217.140.110.172]:34454 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725906AbgCQKGQ (ORCPT ); Tue, 17 Mar 2020 06:06:16 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 8E4891FB; Tue, 17 Mar 2020 03:06:15 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8DD5D3F52E; Tue, 17 Mar 2020 03:06:14 -0700 (PDT) Date: Tue, 17 Mar 2020 10:06:09 +0000 From: Mark Rutland To: Gavin Shan , catalin.marinas@arm.com Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, will@kernel.org, maz@kernel.org, shan.gavin@gmail.com Subject: Re: [PATCH] arm64/kernel: Simplify __cpu_up() by bailing out early Message-ID: <20200317100608.GA8831@lakrids.cambridge.arm.com> References: <20200302020340.119588-1-gshan@redhat.com> <20200302122135.GB56497@lakrids.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200302122135.GB56497@lakrids.cambridge.arm.com> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 02, 2020 at 12:21:35PM +0000, Mark Rutland wrote: > On Mon, Mar 02, 2020 at 01:03:40PM +1100, Gavin Shan wrote: > > The function __cpu_up() is invoked to bring up the target CPU through > > the backend, PSCI for example. The nested if statements won't be needed > > if we bail out early on the following two conditions where the status > > won't be checked. The code looks simplified in that case. > > > > * Error returned from the backend (e.g. PSCI) > > * The target CPU has been marked as onlined > > > > Signed-off-by: Gavin Shan > > FWIW, this looks like a nice cleanup to me: > > Reviewed-by: Mark Rutland Catalin, are you happy to pick this up? Thanks, Mark. > While this patch leaves secondary_data.{task,stack} stale on a > successful onlining, that was already the case for a timeout, and should > be fine (since the next attempt at onlining will configure those before > poking the CPU). > > Thanks, > Mark. > > > --- > > arch/arm64/kernel/smp.c | 79 +++++++++++++++++++---------------------- > > 1 file changed, 37 insertions(+), 42 deletions(-) > > > > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c > > index d4ed9a19d8fe..2a9d8f39dc58 100644 > > --- a/arch/arm64/kernel/smp.c > > +++ b/arch/arm64/kernel/smp.c > > @@ -115,60 +115,55 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle) > > update_cpu_boot_status(CPU_MMU_OFF); > > __flush_dcache_area(&secondary_data, sizeof(secondary_data)); > > > > - /* > > - * Now bring the CPU into our world. > > - */ > > + /* Now bring the CPU into our world */ > > ret = boot_secondary(cpu, idle); > > - if (ret == 0) { > > - /* > > - * CPU was successfully started, wait for it to come online or > > - * time out. > > - */ > > - wait_for_completion_timeout(&cpu_running, > > - msecs_to_jiffies(5000)); > > - > > - if (!cpu_online(cpu)) { > > - pr_crit("CPU%u: failed to come online\n", cpu); > > - ret = -EIO; > > - } > > - } else { > > + if (ret) { > > pr_err("CPU%u: failed to boot: %d\n", cpu, ret); > > return ret; > > } > > > > + /* > > + * CPU was successfully started, wait for it to come online or > > + * time out. > > + */ > > + wait_for_completion_timeout(&cpu_running, > > + msecs_to_jiffies(5000)); > > + if (cpu_online(cpu)) > > + return 0; > > + > > + pr_crit("CPU%u: failed to come online\n", cpu); > > secondary_data.task = NULL; > > secondary_data.stack = NULL; > > __flush_dcache_area(&secondary_data, sizeof(secondary_data)); > > status = READ_ONCE(secondary_data.status); > > - if (ret && status) { > > - > > - if (status == CPU_MMU_OFF) > > - status = READ_ONCE(__early_cpu_boot_status); > > + if (status == CPU_MMU_OFF) > > + status = READ_ONCE(__early_cpu_boot_status); > > > > - switch (status & CPU_BOOT_STATUS_MASK) { > > - default: > > - pr_err("CPU%u: failed in unknown state : 0x%lx\n", > > - cpu, status); > > - cpus_stuck_in_kernel++; > > - break; > > - case CPU_KILL_ME: > > - if (!op_cpu_kill(cpu)) { > > - pr_crit("CPU%u: died during early boot\n", cpu); > > - break; > > - } > > - pr_crit("CPU%u: may not have shut down cleanly\n", cpu); > > - /* Fall through */ > > - case CPU_STUCK_IN_KERNEL: > > - pr_crit("CPU%u: is stuck in kernel\n", cpu); > > - if (status & CPU_STUCK_REASON_52_BIT_VA) > > - pr_crit("CPU%u: does not support 52-bit VAs\n", cpu); > > - if (status & CPU_STUCK_REASON_NO_GRAN) > > - pr_crit("CPU%u: does not support %luK granule \n", cpu, PAGE_SIZE / SZ_1K); > > - cpus_stuck_in_kernel++; > > + switch (status & CPU_BOOT_STATUS_MASK) { > > + default: > > + pr_err("CPU%u: failed in unknown state : 0x%lx\n", > > + cpu, status); > > + cpus_stuck_in_kernel++; > > + break; > > + case CPU_KILL_ME: > > + if (!op_cpu_kill(cpu)) { > > + pr_crit("CPU%u: died during early boot\n", cpu); > > break; > > - case CPU_PANIC_KERNEL: > > - panic("CPU%u detected unsupported configuration\n", cpu); > > } > > + pr_crit("CPU%u: may not have shut down cleanly\n", cpu); > > + /* Fall through */ > > + case CPU_STUCK_IN_KERNEL: > > + pr_crit("CPU%u: is stuck in kernel\n", cpu); > > + if (status & CPU_STUCK_REASON_52_BIT_VA) > > + pr_crit("CPU%u: does not support 52-bit VAs\n", cpu); > > + if (status & CPU_STUCK_REASON_NO_GRAN) { > > + pr_crit("CPU%u: does not support %luK granule\n", > > + cpu, PAGE_SIZE / SZ_1K); > > + } > > + cpus_stuck_in_kernel++; > > + break; > > + case CPU_PANIC_KERNEL: > > + panic("CPU%u detected unsupported configuration\n", cpu); > > } > > > > return ret; > > -- > > 2.23.0 > >