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 3C577C433EF for ; Wed, 3 Nov 2021 17:16:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 162FC6109F for ; Wed, 3 Nov 2021 17:16:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229698AbhKCRTd (ORCPT ); Wed, 3 Nov 2021 13:19:33 -0400 Received: from mga12.intel.com ([192.55.52.136]:53002 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229621AbhKCRTc (ORCPT ); Wed, 3 Nov 2021 13:19:32 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10157"; a="211602890" X-IronPort-AV: E=Sophos;i="5.87,206,1631602800"; d="scan'208";a="211602890" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Nov 2021 10:07:31 -0700 X-IronPort-AV: E=Sophos;i="5.87,206,1631602800"; d="scan'208";a="501172609" Received: from smile.fi.intel.com ([10.237.72.184]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Nov 2021 10:07:29 -0700 Received: from andy by smile.fi.intel.com with local (Exim 4.95) (envelope-from ) id 1miJjF-003K4I-P2; Wed, 03 Nov 2021 19:07:13 +0200 Date: Wed, 3 Nov 2021 19:07:13 +0200 From: Andy Shevchenko To: Petr Mladek Cc: John Ogness , Sakari Ailus , linux-acpi@vger.kernel.org, rafael@kernel.org, mika.westerberg@linux.intel.com 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: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Wed, Nov 03, 2021 at 04:47:44PM +0100, Petr Mladek wrote: > On Wed 2021-11-03 15:50:04, John Ogness wrote: > > 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. Not sure how I may help here, but if there is a requirement to all *printf() to be non-sleepable, then yes, this should be done in that way. I'm not sure if every single %p extension does this... It may require to update fwnode (source code) documentation to reflect the requirement. Also might_sleep() / migth_sleep_if() in the API calls may shed a light on (potential) issues. -- With Best Regards, Andy Shevchenko