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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E6C7AC433EF for ; Tue, 8 Mar 2022 21:15:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350377AbiCHVP7 (ORCPT ); Tue, 8 Mar 2022 16:15:59 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50386 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234717AbiCHVP5 (ORCPT ); Tue, 8 Mar 2022 16:15:57 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7025E43AD5 for ; Tue, 8 Mar 2022 13:15:00 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 14438B81D86 for ; Tue, 8 Mar 2022 21:14:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3955AC340EB; Tue, 8 Mar 2022 21:14:57 +0000 (UTC) Date: Tue, 8 Mar 2022 16:14:55 -0500 From: Steven Rostedt To: Peter Zijlstra Cc: LKML , Thomas Gleixner , Sebastian Andrzej Siewior Subject: sched_core_balance() releasing interrupts with pi_lock held Message-ID: <20220308161455.036e9933@gandalf.local.home> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Peter, A ChromeOS bug report showed a lockdep splat that I first thought was a bad backport. But when looking at upstream, I don't see how it would work there either. The lockdep splat had: [56064.673346] Call Trace: [56064.676066] dump_stack+0xb9/0x117 [56064.679861] ? print_usage_bug+0x2af/0x2c2 [56064.684434] mark_lock_irq+0x25e/0x27d [56064.688618] mark_lock+0x11a/0x16c [56064.692412] mark_held_locks+0x57/0x87 [56064.696595] ? _raw_spin_unlock_irq+0x2c/0x40 [56064.701460] lockdep_hardirqs_on+0xb1/0x19d [56064.706130] _raw_spin_unlock_irq+0x2c/0x40 [56064.710799] sched_core_balance+0x8a/0x4af [56064.715369] ? __balance_callback+0x1f/0x9a [56064.720030] __balance_callback+0x4f/0x9a [56064.724506] rt_mutex_setprio+0x43a/0x48b [56064.728982] task_blocks_on_rt_mutex+0x14d/0x1d5 Where I see: task_blocks_on_rt_mutex() { spin_lock(pi_lock); rt_mutex_setprio() { balance_callback() { sched_core_balance() { spin_unlock_irq(rq); Where spin_unlock_irq() enables interrupts while holding the pi_lock, and BOOM, lockdep (rightfully) complains. The above was me looking at mainline, not the kernel that blew up. So, I'm guessing that this is a bug in mainline as well. -- Steve