From patchwork Thu Jun 23 17:54:48 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Geoff Levand X-Patchwork-Id: 9195683 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 511E1608A0 for ; Thu, 23 Jun 2016 17:57:23 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3FE392845F for ; Thu, 23 Jun 2016 17:57:23 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 32EAA28467; Thu, 23 Jun 2016 17:57:23 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id D19DA28466 for ; Thu, 23 Jun 2016 17:57:22 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.85_2 #1 (Red Hat Linux)) id 1bG8r4-0007p3-2h; Thu, 23 Jun 2016 17:55:54 +0000 Received: from merlin.infradead.org ([2001:4978:20e::2]) by bombadil.infradead.org with esmtps (Exim 4.85_2 #1 (Red Hat Linux)) id 1bG8q4-0005sO-M2; Thu, 23 Jun 2016 17:54:52 +0000 Received: from geoff by merlin.infradead.org with local (Exim 4.85_2 #1 (Red Hat Linux)) id 1bG8q0-0003Qq-4s; Thu, 23 Jun 2016 17:54:48 +0000 Message-Id: <938f5ec9deff917f8e4ad276c01b5c753b7ee83a.1466702804.git.geoff@infradead.org> In-Reply-To: References: From: Geoff Levand Patch-Date: Wed, 22 Jun 2016 10:06:12 +0100 Subject: [PATCH v20 02/14] arm64: smp: Add function to determine if cpus are stuck in the kernel To: Catalin Marinas , Will Deacon Date: Thu, 23 Jun 2016 17:54:48 +0000 X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , marc.zyngier@arm.com, kexec@lists.infradead.org, AKASHI Takahiro , James Morse , linux-arm-kernel@lists.infradead.org MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP From: James Morse kernel/smp.c has a fancy counter that keeps track of the number of CPUs it marked as not-present and left in cpu_park_loop(). If there are any CPUs spinning in here, features like kexec or hibernate may release them by overwriting this memory. This problem also occurs on machines using spin-tables to release secondary cores. After commit 44dbcc93ab67 ("arm64: Fix behavior of maxcpus=N") we bring all known cpus into the secondary holding pen, meaning this memory can't be re-used by kexec or hibernate. Add a function cpus_are_stuck_in_kernel() to determine if either of these cases have occurred. Signed-off-by: James Morse Acked-by: Mark Rutland Reviewed-by: Suzuki K Poulose --- arch/arm64/include/asm/smp.h | 12 ++++++++++++ arch/arm64/kernel/smp.c | 18 ++++++++++++++++++ 2 files changed, 30 insertions(+) diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h index 433e504..0226447 100644 --- a/arch/arm64/include/asm/smp.h +++ b/arch/arm64/include/asm/smp.h @@ -124,6 +124,18 @@ static inline void cpu_panic_kernel(void) cpu_park_loop(); } +/* + * If a secondary CPU enters the kernel but fails to come online, + * (e.g. due to mismatched features), and cannot exit the kernel, + * we increment cpus_stuck_in_kernel and leave the CPU in a + * quiesecent loop within the kernel text. The memory containing + * this loop must not be re-used for anything else as the 'stuck' + * core is executing it. + * + * This function is used to inhibit features like kexec and hibernate. + */ +bool cpus_are_stuck_in_kernel(void); + #endif /* ifndef __ASSEMBLY__ */ #endif /* ifndef __ASM_SMP_H */ diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index 678e084..62ff3c0 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -909,3 +909,21 @@ int setup_profiling_timer(unsigned int multiplier) { return -EINVAL; } + +static bool have_cpu_die(void) +{ +#ifdef CONFIG_HOTPLUG_CPU + int any_cpu = raw_smp_processor_id(); + + if (cpu_ops[any_cpu]->cpu_die) + return true; +#endif + return false; +} + +bool cpus_are_stuck_in_kernel(void) +{ + bool smp_spin_tables = (num_possible_cpus() > 1 && !have_cpu_die()); + + return !!cpus_stuck_in_kernel || smp_spin_tables; +}