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=-9.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS, T_DKIMWL_WL_HIGH,USER_AGENT_GIT 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 7BD21C43219 for ; Thu, 2 May 2019 19:16:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4F59A214DA for ; Thu, 2 May 2019 19:16:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556824570; bh=zTKiB59yTAOgeXBzuwna1gvCfKgXqxqkpL/Tomsj28c=; h=From:To:Subject:Date:In-Reply-To:References:In-Reply-To: References:List-ID:From; b=hMciL3nT5mdYpmsnOPIzYL+yK1KvGy4u1fKxdRluECHo1K3R+tGmMPiZf+7nsb21d 01gqaogYe95+SrzuSJCjbfENMd4jLRjkktT2j1ZOahRx8/9kx1pKikNl0f4Mkwa1QU ihNgDCuvbrmvBPUSlGtgylI+D/LjJ0/7FVt7j4NI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726552AbfEBTQI (ORCPT ); Thu, 2 May 2019 15:16:08 -0400 Received: from mail.kernel.org ([198.145.29.99]:33266 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726510AbfEBTQF (ORCPT ); Thu, 2 May 2019 15:16:05 -0400 Received: from localhost.localdomain (c-98-220-238-81.hsd1.il.comcast.net [98.220.238.81]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C52962133F; Thu, 2 May 2019 19:16:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556824564; bh=zTKiB59yTAOgeXBzuwna1gvCfKgXqxqkpL/Tomsj28c=; h=From:To:Subject:Date:In-Reply-To:References:In-Reply-To: References:From; b=ekPBI3vq7auZZwdZAild0WCJENM03KV6CnckxH933Qnzjv5Zl2jn2Ai4o+Y3HHvny ujCQFwFfRrInuGl0HmX7gDDv25/vkPyonq6hrwCUCSGyXXyxAfNAq13Vhh/u7qcMDG q077FNxphmKvNqejhVkUKyWnsWZWLX4ZeSSPgPm0= From: zanussi@kernel.org To: LKML , linux-rt-users , Steven Rostedt , Thomas Gleixner , Carsten Emde , John Kacur , Sebastian Andrzej Siewior , Daniel Wagner , Tom Zanussi , Julia Cartwright Subject: [PATCH RT 3/4] tty/sysrq: Convert show_lock to raw_spinlock_t Date: Thu, 2 May 2019 14:15:38 -0500 Message-Id: <7433082948d7d5062f1d3fbbcae07616a8e07a98.1556824516.git.tom.zanussi@linux.intel.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Julien Grall v3.18.138-rt116-rc1 stable review patch. If anyone has any objections, please let me know. ----------- [ Upstream commit db80c207bffd0f49e984e9889ce62279bc3abd6c ] Systems which don't provide arch_trigger_cpumask_backtrace() will invoke showacpu() from a smp_call_function() function which is invoked with disabled interrupts even on -RT systems. The function acquires the show_lock lock which only purpose is to ensure that the CPUs don't print simultaneously. Otherwise the output would clash and it would be hard to tell the output from CPUx apart from CPUy. On -RT the spin_lock() can not be acquired from this context. A raw_spin_lock() is required. It will introduce the system's latency by performing the sysrq request and other CPUs will block on the lock until the request is done. This is okay because the user asked for a backtrace of all active CPUs and under "normal circumstances in production" this path should not be triggered. Signed-off-by: Julien Grall [bigeasy@linuxtronix.de: commit description] Signed-off-by: Sebastian Andrzej Siewior Acked-by: Sebastian Andrzej Siewior Signed-off-by: Greg Kroah-Hartman Cc: stable-rt@vger.kernel.org Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Tom Zanussi Conflicts: drivers/tty/sysrq.c --- drivers/tty/sysrq.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c index f97e7dac3a98..36ed02aa5575 100644 --- a/drivers/tty/sysrq.c +++ b/drivers/tty/sysrq.c @@ -206,7 +206,7 @@ static struct sysrq_key_op sysrq_showlocks_op = { #endif #ifdef CONFIG_SMP -static DEFINE_SPINLOCK(show_lock); +static DEFINE_RAW_SPINLOCK(show_lock); static void showacpu(void *dummy) { @@ -216,10 +216,10 @@ static void showacpu(void *dummy) if (idle_cpu(smp_processor_id())) return; - spin_lock_irqsave(&show_lock, flags); + raw_spin_lock_irqsave(&show_lock, flags); printk(KERN_INFO "CPU%d:\n", smp_processor_id()); show_stack(NULL, NULL); - spin_unlock_irqrestore(&show_lock, flags); + raw_spin_unlock_irqrestore(&show_lock, flags); } static void sysrq_showregs_othercpus(struct work_struct *dummy) -- 2.14.1