From patchwork Thu May 30 11:30:58 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Julien Grall X-Patchwork-Id: 165440 Delivered-To: patch@linaro.org Received: by 2002:a92:9e1a:0:0:0:0:0 with SMTP id q26csp839977ili; Thu, 30 May 2019 04:31:11 -0700 (PDT) X-Google-Smtp-Source: APXvYqzbZs30wwpYOngJtPa89iUDodQwd64fAP+FH2mA2bcRe4ziGBsvMBXsL1R66dWtcP97F6LH X-Received: by 2002:a62:2506:: with SMTP id l6mr3255634pfl.250.1559215871814; Thu, 30 May 2019 04:31:11 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1559215871; cv=none; d=google.com; s=arc-20160816; b=GuxtbIdU5ruHeYLkHl1o4tBgcTYaFEnMGgvKEsUGO0UP7iQFUDFQUHtt+e3eNgOskG aIRdSUrRCUeQQRPHfkM6ik2xlDHWZQFtMh+5oUWe/ZyjxhwNuTINyvKtjYOZ19wEmTU4 1YnuH+YL1UILAh2D/6twoLcgxT0gllCI9VJf0VMSKchbszOA1fTkcxA1qAEXZtM9vxIZ dJeu+iNJjFen3Zi6x07Q8+kckWJxBvotNdiLb4Wb/hiOliMz84zXW3tfq1VgK4zfDU0/ 4LkMAYDDm2/MKZyBszof0gYXvoiZd8xnlDBFsMY9Al96oZdsNRDhlI5LWRjNCQV0oyML 6DWA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:message-id:date:subject:cc:to:from; bh=VwaM2pLRqHnMfXTK1+k1JSOH5oZQCCOeXSWQL1WCaz4=; b=hWx7DRnBaRYUDiMOvf7DJAz09+msreUMgnR+ZaS2OAmLLYpndRT5RpnUPqWUOBmDHu sWkDkDCUXMwC3i1BqA3x75icFKV8f6N21hZwGQCuAJEbaYl0ECnahS+Bim1yyjKWHHlw fNMYjW6yt++NCMn6IzsriwlCC7RNlxocR35a2UPpvIzTWrcb1DaPdtEMkzIIWN6tv3Mx 10yjCXU9Mb08iCERuh1TRklX1DWhJsgnuMRCLyOD92lvXjeOWkBAxqyRR6HlGKoDBEH6 ttdxkS3n8bj/h48zzaPasckdqAMO3Z7K2lr3urshb+HPUMG7xlBWxJ8sT2GTMTQe47P1 5lzg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id x11si2758590pgh.222.2019.05.30.04.31.11; Thu, 30 May 2019 04:31:11 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726549AbfE3LbK (ORCPT + 30 others); 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-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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(-) -- 2.11.0 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);