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_PASS,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 0FD74C43381 for ; Mon, 4 Mar 2019 17:21:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D99C5206B8 for ; Mon, 4 Mar 2019 17:21:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727136AbfCDRVA (ORCPT ); Mon, 4 Mar 2019 12:21:00 -0500 Received: from foss.arm.com ([217.140.101.70]:36322 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726098AbfCDRVA (ORCPT ); Mon, 4 Mar 2019 12:21:00 -0500 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 979BBA78; Mon, 4 Mar 2019 09:20:59 -0800 (PST) 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 8714C3F703; Mon, 4 Mar 2019 09:20:58 -0800 (PST) From: Julien Grall To: linux-kernel@vger.kernel.org Cc: jslaby@suse.com, gregkh@linuxfoundation.org, linux-rt-users@vger.kernel.ort, Julien Grall Subject: [PATCH] tty/sysrq: Convert show_lock to raw_spinlock_t Date: Mon, 4 Mar 2019 17:20:53 +0000 Message-Id: <20190304172053.17340-1-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 At the moment show_lock is implemented using spin_lock_t and called from an interrupt context on Arm64. The following backtrace was triggered by: 42sh# echo l > /proc/sysrq-trigger [ 4432.073756] sysrq: SysRq : Show backtrace of all active CPUs [ 4432.403422] BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:974 [ 4432.403424] sysrq: CPU6: [ 4432.403426] in_atomic(): 1, irqs_disabled(): 128, pid: 2410, name: kworker/u16:2 [...] [ 4432.403581] Call trace: [ 4432.403584] dump_backtrace+0x0/0x148 [ 4432.403586] show_stack+0x14/0x20 [ 4432.403588] dump_stack+0x9c/0xd4 [ 4432.403592] ___might_sleep+0x1cc/0x298 [ 4432.403595] rt_spin_lock+0x5c/0x70 [ 4432.403596] showacpu+0x34/0x68 [ 4432.403599] flush_smp_call_function_queue+0xd4/0x278 [ 4432.403602] generic_smp_call_function_single_interrupt+0x10/0x18 [ 4432.403605] handle_IPI+0x26c/0x668 [ 4432.403607] gic_handle_irq+0x9c/0xa0 [ 4432.403609] el1_irq+0xb4/0x13c With RT-patches, spin_lock can now sleep and therefore cannot be used from interrupt context. Use a raw_spin_lock instead to prevent the lock to sleep. Signed-off-by: Julien Grall --- 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 1f03078ec352..8473557c7ab2 100644 --- a/drivers/tty/sysrq.c +++ b/drivers/tty/sysrq.c @@ -208,7 +208,7 @@ 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) { @@ -218,10 +218,10 @@ 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); pr_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) -- 2.11.0