Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932650AbcLAXQO (ORCPT ); Thu, 1 Dec 2016 18:16:14 -0500 Received: from xes-mad.com ([216.165.139.218]:59421 "EHLO xes-mad.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756087AbcLAXQM (ORCPT ); Thu, 1 Dec 2016 18:16:12 -0500 Date: Thu, 1 Dec 2016 17:16:00 -0600 (CST) From: Aaron Sierra To: Thomas Gleixner Cc: Sebastian Andrzej Siewior , Steven Rostedt , linux-kernel Message-ID: <1883606374.779009.1480634160092.JavaMail.zimbra@xes-inc.com> In-Reply-To: References: <390489414.497553.1480534166735.JavaMail.zimbra@xes-inc.com> Subject: Re: [PATCH] acpi/rt: convert acpi_gbl_gpe_lock to raw spinlock MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Originating-IP: [10.52.0.127] X-Mailer: Zimbra 8.7.0_GA_1659 (ZimbraWebClient - FF48 (Linux)/8.7.0_GA_1659) Thread-Topic: acpi/rt: convert acpi_gbl_gpe_lock to raw spinlock Thread-Index: K0AkLhkYC1DfnO6SK5ZfDQq4Lk5UCQ== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2637 Lines: 61 ----- Original Message ----- > From: "Thomas Gleixner" > Sent: Thursday, December 1, 2016 8:52:48 AM > On Wed, 30 Nov 2016, Aaron Sierra wrote: >> When testing GPE interrupts with CONFIG_PREEMPT_RT_FULL enabled, a >> verbose WARN_ONCE message would print to the kernel log. It turned out >> that the GPE interrupt handler was being called with local interrupts >> enabled because acpi_gbl_gpe_lock was implemented as a spinlock_t. Full >> preemption strips local interrupt disabling from spinlock_t operations, >> but not for raw_spinlock_t operations. >> >> This is the warning that was triggered: >> >> ------------[ cut here ]------------ >> WARNING: CPU: 8 PID: 483 at kernel/irq/handle.c:149 >> __handle_irq_event_percpu+0x6f/0xcf >> irq 33 handler irq_default_primary_handler+0x0/0xb enabled interrupts >> Modules linked in: gpio_irq_demo(O) >> CPU: 8 PID: 483 Comm: irq/9-acpi Tainted: G O >> 4.8.6-rt5-00012-geaa3b7c #6 >> Hardware name: Extreme Engineering Solutions, Inc. XCalibur4643/XCalibur4643, >> BIOS 1-1.1.12.3_Alpha 04/29/2016 >> 0000000000000000 ffff880858f3bc10 ffffffff81219a93 ffff880858f3bc60 >> 0000000000000000 ffff880858f3bc50 ffffffff8104b84a 0000009500000000 >> ffff880855b76880 0000000000000021 0000000000000002 ffff880856356800 >> Call Trace: >> [] dump_stack+0x4d/0x63 >> [] __warn+0xc0/0xdb >> [] warn_slowpath_fmt+0x4a/0x4c >> [] ? path_openat+0xbf8/0xc62 >> [] ? handle_irq_event+0x75/0x75 >> [] __handle_irq_event_percpu+0x6f/0xcf >> [] handle_irq_event_percpu+0x3a/0x61 >> [] handle_irq_event+0x55/0x75 >> [] handle_simple_irq+0x5c/0x92 >> [] gpe_irq_handler+0x2a/0x31 > > gpe_irq_handler is not in tree, so I really cannot tell what this is > about. It looks like it does interrupt demultiplexing, which triggers the > warning. Thomas, Your guess is correct, this involves a currently out-of-tree extension to the gpio-ich driver which allows GPIO pins to be mapped to IRQs by demuxing their corresponding GPE events. The gpio_irq_demo module requests a GPIO pin, converts it to an IRQ using gpio_to_irq() and registers a trivial handler against the IRQ. > We tried to make that lock raw years ago and this results in a different > splat: https://marc.info/?l=linux-kernel&m=132468512523207&w=2 Thanks for the background. > So no, we are not making that lock raw again blindly just because of random > out of tree code. I thought that might be that case. -Aaron S.