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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7B948F33806 for ; Tue, 17 Mar 2026 07:10:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=aGqp2eGvZ8eiDb2PfS0r3jiP1qfEAOp2TvAsRj299EU=; b=e7KnNEkUkpwTtrSffHg0qCXER1 v4T8XHddAJRnRQ51KFr1nMyodsw/UG0MWB9iKaYMjT74/KIYSpDr2gJLbt6FX0v34WYlQ23D8xePy /299InaX5YBMivMmCA809oQdZaDi90Wv3y+PywrFXMxKbyxWIEhRmzZwNVeyFcN5ZCwA/fa1ABf21 5zljbmaoK5q7I2/E6fRDUJ58Lw+IVRpQfWIM+LfhqhIU3FT1l7NtYdQpoUiQQjEMo0LSmE/kf63ly 8rqg9cVcWNNUuzCkWqYuaaPtlyuXYwOulNxwIjxZrcAMTDiuPPaDYTO4t0BQc8pBd1tWtzG7tXB2S 02hSF+5Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1w2OZj-00000005Y2D-1j7m; Tue, 17 Mar 2026 07:10:47 +0000 Received: from mgamail.intel.com ([198.175.65.10]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1w2OZe-00000005Y1j-2WTm for linux-arm-kernel@lists.infradead.org; Tue, 17 Mar 2026 07:10:45 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1773731443; x=1805267443; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=R7+uigS6RvsoYyWW802Gylu1VZG5usDe19K1H9gY0l4=; b=nY+Yp5tB2zEwQcbqcgUffRsoA79CVvHNJMnqiWNodEVR0U4st6WnmDGZ 4vy+tFsRS2Zd+poppTH6O3ghiTM7HnWRZPA2ahaf17fGTlVXpEuph9EUf 9WKNuHztrkhzarle+nfiCIhametCPhdsfOqSZCKTNzW4zSThLRdZ3wakU /HqAsMBEg+KhDSsHrM5hTJ0+n9KZeIuMS7TzbpW1+k7x/eIiyO3mfatXQ tNivYIMhOsBIaOfxOU/MkfA12ESPLCo8VzoEePGlxGAc9JkKdiZPr+Erj ljM2FTBqcAKVvJaaCivsLi0PyWUwqErIwIlFOuuauc1KcIMHfre+nKpFF A==; X-CSE-ConnectionGUID: a7mX+YXPRpaNDI+2hyGv3A== X-CSE-MsgGUID: oTKA4YNgR+iyVAO1V967zQ== X-IronPort-AV: E=McAfee;i="6800,10657,11731"; a="92138495" X-IronPort-AV: E=Sophos;i="6.23,124,1770624000"; d="scan'208";a="92138495" Received: from orviesa006.jf.intel.com ([10.64.159.146]) by orvoesa102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Mar 2026 00:10:37 -0700 X-CSE-ConnectionGUID: 8SCEUEfxRtmk1tqABg3+qA== X-CSE-MsgGUID: nY7xou3+QbiCy45uqFfElw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.23,124,1770624000"; d="scan'208";a="221200793" Received: from abityuts-desk.ger.corp.intel.com (HELO localhost) ([10.245.245.97]) by orviesa006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Mar 2026 00:10:28 -0700 Date: Tue, 17 Mar 2026 09:10:26 +0200 From: Andy Shevchenko To: Douglas Anderson Cc: Greg Kroah-Hartman , "Rafael J . Wysocki" , Danilo Krummrich , stable@vger.kernel.org, Andrew Lunn , Daniel Scally , "David S. Miller" , Eric Dumazet , Fabio Estevam , Frank Li , Heikki Krogerus , Heiner Kallweit , Jakub Kicinski , Len Brown , Mark Brown , Paolo Abeni , Pengutronix Kernel Team , Rob Herring , Russell King , Sakari Ailus , Saravana Kannan , Sascha Hauer , Wolfram Sang , devicetree@vger.kernel.org, driver-core@lists.linux.dev, imx@lists.linux.dev, linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH] device property: Make modifications of fwnode "flags" thread safe Message-ID: References: <20260316154159.1.I0a4d03104ecd5103df3d76f66c8d21b1d15a2e38@changeid> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260316154159.1.I0a4d03104ecd5103df3d76f66c8d21b1d15a2e38@changeid> Organization: Intel Finland Oy - BIC 0357606-4 - c/o Alberga Business Park, 6 krs, Bertel Jungin Aukio 5, 02600 Espoo X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260317_001042_683643_DCED51D3 X-CRM114-Status: GOOD ( 21.30 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Mar 16, 2026 at 03:42:06PM -0700, Douglas Anderson wrote: > In various places in the kernel, we modify the fwnode "flags" member > by doing either: > fwnode->flags |= SOME_FLAG; > fwnode->flags &= ~SOME_FLAG; > > This type of modification is not thread-safe. If two threads are both > mucking with the flags at the same time then one can clobber the > other. > > While flags are often modified while under the "fwnode_link_lock", > this is not universally true. > > Create some accessor functions for setting, clearing, and testing the > FWNODE flags and move all users to these accessor functions. New > accessor functions use set_bit() and clear_bit(), which are > thread-safe. In general I like the idea (independently on the treewide patch or a series). Reviewed-by: Andy Shevchenko See one nit-pick below, though. ... > While this patch is not known for sure to fix any specific issues, it > seems possible that it could fix some rare problems. I'm currently > trying to track down a hard-to-reproduce heisenbug and one (currently > unproven) theory I had was that the fwnode flags could be getting > messed up like this. Even if turns out not to fix my heisenbug, > though, this seems like a worthwhile change to take. Totally agree. This makes code more OOP like and robust against subtle modifications. ... > +static inline void fwnode_set_flag(struct fwnode_handle *fwnode, > + unsigned int bit) > +{ > + set_bit(bit, &fwnode->flags); > +} > + > +static inline void fwnode_clear_flag(struct fwnode_handle *fwnode, > + unsigned int bit) > +{ > + clear_bit(bit, &fwnode->flags); > +} Perhaps you also want to have fwnode_assign_flag() (assign_bit() underneath) as... > +static inline bool fwnode_test_flag(struct fwnode_handle *fwnode, > + unsigned int bit) > +{ > + return test_bit(bit, &fwnode->flags); > +} > if (initialized) > - fwnode->flags |= FWNODE_FLAG_INITIALIZED; > + fwnode_set_flag(fwnode, FWNODE_FLAG_INITIALIZED); > else > - fwnode->flags &= ~FWNODE_FLAG_INITIALIZED; > + fwnode_clear_flag(fwnode, FWNODE_FLAG_INITIALIZED); ...at least one immediate user here. -- With Best Regards, Andy Shevchenko