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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 880E2C282D7 for ; Wed, 30 Jan 2019 18:21:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 612EC2087F for ; Wed, 30 Jan 2019 18:21:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733019AbfA3SVc (ORCPT ); Wed, 30 Jan 2019 13:21:32 -0500 Received: from foss.arm.com ([217.140.101.70]:59648 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1733006AbfA3SVc (ORCPT ); Wed, 30 Jan 2019 13:21:32 -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 E7A9E80D; Wed, 30 Jan 2019 10:21:31 -0800 (PST) Received: from fuggles.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B51CE3F557; Wed, 30 Jan 2019 10:21:30 -0800 (PST) Date: Wed, 30 Jan 2019 18:21:28 +0000 From: Will Deacon To: "Li, Meng" Cc: "mark.rutland@arm.com" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , suzuki.poulose@arm.com, robin.murphy@arm.com Subject: Re: Could you please help to have a look a bug trace in pmu arm-cci.c Message-ID: <20190130182128.GM18558@fuggles.cambridge.arm.com> References: <529F9A9100AE8045A7A5B5A00A39FBB862099B8E@ALA-MBD.corp.ad.wrs.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <529F9A9100AE8045A7A5B5A00A39FBB862099B8E@ALA-MBD.corp.ad.wrs.com> User-Agent: Mutt/1.11.1+86 (6f28e57d73f2) () Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [+Suzuki and Robin] On Mon, Jan 28, 2019 at 07:19:20AM +0000, Li, Meng wrote: > When enable kernel configure CONFIG_DEBUG_ATOMIC_SLEEP, there is below trace > during pmu arm cci driver probe phase. > > [ 1.983337] BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:2004 > [ 1.983340] in_atomic(): 1, irqs_disabled(): 0, pid: 1, name: swapper/0 > [ 1.983342] Preemption disabled at: > [ 1.983353] [] cci_pmu_probe+0x1dc/0x488 > [ 1.983360] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.18.20-rt8-yocto-preempt-rt #1 > [ 1.983362] Hardware name: ZynqMP ZCU102 Rev1.0 (DT) > [ 1.983364] Call trace: > [ 1.983369] dump_backtrace+0x0/0x158 > [ 1.983372] show_stack+0x24/0x30 > [ 1.983378] dump_stack+0x80/0xa4 > [ 1.983383] ___might_sleep+0x138/0x160 > [ 1.983386] __might_sleep+0x58/0x90 > [ 1.983391] __rt_mutex_lock_state+0x30/0xc0 > [ 1.983395] _mutex_lock+0x24/0x30 > [ 1.983400] perf_pmu_register+0x2c/0x388 > [ 1.983404] cci_pmu_probe+0x2bc/0x488 > [ 1.983409] platform_drv_probe+0x58/0xa8 > > Because get_cpu() is invoked, preempt is disable, finally, trace occurs when > call might_sleep() Hmm, the {get,put}_cpu() usage here looks very broken to me. There's the fact that it might sleep, but also the assignment to g_cci_pmu is done after we've re-enabled preemption, so there's a race with CPU hotplug there too. I don't think we can simply register the hotplug notifier before registering the PMU, because we can't call into perf_pmu_migrate_context() until the PMU has been registered. Perhaps we need to use the _cpuslocked() versions of the hotplug notifier registration functions. I tried looking at some other drivers, but they all look broken to me, so there's a good chance I'm missing something. Anybody know how this is supposed to work? Will