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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 0933DC28CC0 for ; Thu, 30 May 2019 11:31:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E1A862585A for ; Thu, 30 May 2019 11:31:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726232AbfE3LbK (ORCPT ); Thu, 30 May 2019 07:31:10 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:34700 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726065AbfE3LbK (ORCPT ); Thu, 30 May 2019 07:31:10 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 78B11374; Thu, 30 May 2019 04:31:07 -0700 (PDT) Received: from e108454-lin.cambridge.arm.com (e108454-lin.cambridge.arm.com [10.1.196.50]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 853FF3F5AF; Thu, 30 May 2019 04:31:05 -0700 (PDT) From: Julien Grall To: linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: tglx@linutronix.de, rostedt@goodmis.org, bigeasy@linutronix.de, suzuki.poulose@arm.com, catalin.marinas@arm.com, will.deacon@arm.com, dave.martin@arm.com, Julien Grall Subject: [PATCH] arm64/cpufeature: Convert hook_lock to raw_spin_lock_t in cpu_enable_ssbs() Date: Thu, 30 May 2019 12:30:58 +0100 Message-Id: <20190530113058.1988-1-julien.grall@arm.com> X-Mailer: git-send-email 2.11.0 Sender: linux-rt-users-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org cpu_enable_ssbs() is called via stop_machine() as part of the cpu_enable callback. A spin lock is used to ensure the hook is registered before the rest of the callback is executed. On -RT spin_lock() may sleep. However, all the callees in stop_machine() are expected to not sleep. Therefore a raw_spin_lock() is required here. Given this is already done under stop_machine() and the work done under the lock is quite small, the latency should not increase too much. Signed-off-by: Julien Grall --- It was noticed when looking at the current use of spin_lock in arch/arm64. I don't have a platform calling that callback, so I have hacked the code to reproduce the error and check it is now fixed. --- arch/arm64/kernel/cpufeature.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index ca27e08e3d8a..2a7159fda3ce 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -1194,14 +1194,14 @@ static struct undef_hook ssbs_emulation_hook = { static void cpu_enable_ssbs(const struct arm64_cpu_capabilities *__unused) { static bool undef_hook_registered = false; - static DEFINE_SPINLOCK(hook_lock); + static DEFINE_RAW_SPINLOCK(hook_lock); - spin_lock(&hook_lock); + raw_spin_lock(&hook_lock); if (!undef_hook_registered) { register_undef_hook(&ssbs_emulation_hook); undef_hook_registered = true; } - spin_unlock(&hook_lock); + raw_spin_unlock(&hook_lock); if (arm64_get_ssbd_state() == ARM64_SSBD_FORCE_DISABLE) { sysreg_clear_set(sctlr_el1, 0, SCTLR_ELx_DSSBS); -- 2.11.0