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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0757CC433EF for ; Wed, 3 Nov 2021 15:49:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E22F260E73 for ; Wed, 3 Nov 2021 15:49:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231814AbhKCPvr (ORCPT ); Wed, 3 Nov 2021 11:51:47 -0400 Received: from smtp-out2.suse.de ([195.135.220.29]:58340 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231765AbhKCPvr (ORCPT ); Wed, 3 Nov 2021 11:51:47 -0400 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id C1B3A1FD38; Wed, 3 Nov 2021 15:49:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1635954549; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=UfsSMQ63Ciq0CR8DQZtZN6CvjWxicn8ShNavcOZog8k=; b=OXT0vTWDpUESk8U4Wgk46w3pODBVb9kWEAZUc+Oz+TR6ZM37ywxKCUKDnN8Ozm1ZBYLFVm jvIYy2hZrEt88+5ALWk0lpz+cr/cVikHdP/kbA8z8Sr2YHsUeYIkPZNQxvEegHWQITmyy1 W27U8WfE8B3gPPM9/TFHRJM7F0S9nIc= Received: from suse.cz (unknown [10.100.224.162]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id A4EC32C144; Wed, 3 Nov 2021 15:49:09 +0000 (UTC) Date: Wed, 3 Nov 2021 16:49:07 +0100 From: Petr Mladek To: John Ogness Cc: Sakari Ailus , linux-acpi@vger.kernel.org, rafael@kernel.org, mika.westerberg@linux.intel.com, Andy Shevchenko Subject: Re: [PATCH 0/3] Get device's parent from parent field, fix sleeping IRQs disabled Message-ID: References: <20211103133406.659542-1-sakari.ailus@linux.intel.com> <878ry55mff.fsf@jogness.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <878ry55mff.fsf@jogness.linutronix.de> Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org (and really add Andy) On Wed 2021-11-03 15:50:04, John Ogness wrote: > added CC: printk maintainer (Petr Mladek) > > On 2021-11-03, Sakari Ailus wrote: > > This set changes getting fwnode's parent on ACPI fwnode so it no longer > > needs a semaphore, using struct acpi_device->parent field instead of > > calling acpi_get_parent(). The semaphore is being acquired when the > > device's full path is printed which now takes place local IRQs disabled: > > > > --------8<------------------------ > > BUG: sleeping function called from invalid context at kernel/locking/semaphore.c:163 > > > > ... > > > > Call Trace: > > > > dump_stack_lvl+0x57/0x7d > > __might_resched.cold+0xf4/0x12f > > down_timeout+0x21/0x70 > > acpi_os_wait_semaphore+0x63/0x180 > > acpi_ut_acquire_mutex+0x123/0x1ba > > acpi_get_parent+0x30/0x71 > > acpi_node_get_parent+0x64/0x90 > > ? lock_acquire+0x1a0/0x300 > > fwnode_count_parents+0x6d/0xb0 > > fwnode_full_name_string+0x18/0x90 > > fwnode_string+0xd7/0x140 > > vsnprintf+0x1ec/0x4f0 > > va_format.constprop.0+0x6a/0x130 > > vsnprintf+0x1ec/0x4f0 > > vprintk_store+0x271/0x5a0 > > ? rcu_read_lock_sched_held+0x12/0x70 > > ? lock_release+0x228/0x310 > > ? acpi_initialize_hp_context+0x50/0x50 > > vprintk_emit+0xd5/0x340 > > _printk+0x58/0x6f > ... > > --------8<------------------------ > > > > I guess one could argue it wasn't great to begin with that getting > > fwnode's parent required a semaphore to begin with, nevertheless John's > > patch made it a concrete problem. Added Cc: stable, too. It looks like a generic problem. If I get it properly, we should make sure that any struct fwnode_operations implementation will _not_ use sleeping locks in the .get_parent() callback. Or anything that is called indirectly from from vsprintf. Adding Andy into Cc. > Well, before my work it was vprintk_emit() that was disabling local > interrupts. So this has always been broken. > > Really it should be: > > Fixes: 3bd32d6a2ee6 ("lib/vsprintf: Add %pfw conversion specifier for > printing fwnode names") Yes, I consider this to be the culprit. > Regardless, the fix should go into 5.10 and 5.14 stables. Please add the Fixes tag and the following into the commit message: Cc: stable@vger.kernel.org # v5.5+ Best Regards, Petr