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 71B6CC4167B for ; Tue, 14 Nov 2023 13:13:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230491AbjKNNN0 (ORCPT ); Tue, 14 Nov 2023 08:13:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53182 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231878AbjKNNNZ (ORCPT ); Tue, 14 Nov 2023 08:13:25 -0500 Received: from mgamail.intel.com (mgamail.intel.com [192.55.52.115]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CEEC719D; Tue, 14 Nov 2023 05:13:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1699967601; x=1731503601; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=615MD5nkn7JkyN4xZpVO/ZoKT90VKtVl8ldiXoiXB2c=; b=cJ+9bhNHOKjLLdiOR/gnRC/i+gpQRvAFqlqHVSqPWPXmgYkq8QbN1jYo pkBncVnalYZJ3gV862j6504L9vJcIyCKUMiOQD0Q/9vcj1KwF9zFllrHv xl9nWq+VOTPKhkAEC+ulNZwq2R+yxYcqIe49hpy/6YRJHGxkhmBTheOku 1nb2xoaowculk4dFsADXAYbcct/u+dS5ltcu899vljKUvAYZn9scS1ELS xO2+u+gGzRN3Vfv/AFbFY8/sFnfXqsiqmDwwm5Af/ylhcSzVPzTOWnv9Y aw888/ImheGOXOXP7UJ2wpwe9nSLcEWjLbQrxt023i4ZyydK6OwzdBxgM g==; X-IronPort-AV: E=McAfee;i="6600,9927,10893"; a="390444153" X-IronPort-AV: E=Sophos;i="6.03,302,1694761200"; d="scan'208";a="390444153" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Nov 2023 05:12:54 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10893"; a="855274187" X-IronPort-AV: E=Sophos;i="6.03,302,1694761200"; d="scan'208";a="855274187" Received: from smile.fi.intel.com ([10.237.72.54]) by FMSMGA003.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Nov 2023 05:12:51 -0800 Received: from andy by smile.fi.intel.com with local (Exim 4.97-RC3) (envelope-from ) id 1r2tDj-0000000Dos3-41HX; Tue, 14 Nov 2023 15:12:47 +0200 Date: Tue, 14 Nov 2023 15:12:47 +0200 From: Andy Shevchenko To: Herve Codina Cc: Saravana Kannan , Petr Mladek , Steven Rostedt , Rasmus Villemoes , Sergey Senozhatsky , Sakari Ailus , "Rafael J. Wysocki" , linux-kernel@vger.kernel.org, Allan Nielsen , Horatiu Vultur , Steen Hegelund , Thomas Petazzoni , stable@vger.kernel.org Subject: Re: [PATCH 1/1] lib/vsprintf: Fix %pfwf when current node refcount == 0 Message-ID: References: <20231114110456.273844-1-herve.codina@bootlin.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231114110456.273844-1-herve.codina@bootlin.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 14, 2023 at 12:04:56PM +0100, Herve Codina wrote: > A refcount issue can appeared in __fwnode_link_del() due to the > pr_debug() call: > WARNING: CPU: 0 PID: 901 at lib/refcount.c:25 refcount_warn_saturate+0xe5/0x110 > Call Trace: > > ? refcount_warn_saturate+0xe5/0x110 > ? __warn+0x81/0x130 > ? refcount_warn_saturate+0xe5/0x110 > ? report_bug+0x191/0x1c0 > ? srso_alias_return_thunk+0x5/0x7f > ? prb_read_valid+0x1b/0x30 > ? handle_bug+0x3c/0x80 > ? exc_invalid_op+0x17/0x70 > ? asm_exc_invalid_op+0x1a/0x20 > ? refcount_warn_saturate+0xe5/0x110 > kobject_get+0x68/0x70 > of_node_get+0x1e/0x30 > of_fwnode_get+0x28/0x40 > fwnode_full_name_string+0x34/0x90 > fwnode_string+0xdb/0x140 > vsnprintf+0x17b/0x630 > va_format.isra.0+0x71/0x130 > vsnprintf+0x17b/0x630 > vprintk_store+0x162/0x4d0 > ? srso_alias_return_thunk+0x5/0x7f > ? srso_alias_return_thunk+0x5/0x7f > ? srso_alias_return_thunk+0x5/0x7f > ? try_to_wake_up+0x9c/0x620 > ? rwsem_mark_wake+0x1b2/0x310 > vprintk_emit+0xe4/0x2b0 > _printk+0x5c/0x80 > __dynamic_pr_debug+0x131/0x160 > ? srso_alias_return_thunk+0x5/0x7f > __fwnode_link_del+0x25/0xa0 > fwnode_links_purge+0x39/0xb0 > of_node_release+0xd9/0x180 > kobject_put+0x7b/0x190 > ... Please, do not put so many unrelated lines of backtrace in the commit message. Leave only the important ones (the Submitting Patches document suggests some like ~3-5 lines only). > Indeed, an fwnode (of_node) is being destroyed and so, of_node_release() > is called because the of_node refcount reached 0. > From of_node_release() several function calls are done and lead to > a pr_debug() calls with %pfwf to print the fwnode full name. > The issue is not present if we change %pfwf to %pfwP. > > To print the full name, %pfwf iterates over the current node and its > parents and obtain/drop a reference to all nodes involved. > > In order to allow to print the full name (%pfwf) of a node while it is > being destroyed, do not obtain/drop a reference to this current node. -- With Best Regards, Andy Shevchenko