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 74B1FC43334 for ; Tue, 26 Jul 2022 01:47:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231316AbiGZBru (ORCPT ); Mon, 25 Jul 2022 21:47:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41548 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230033AbiGZBrt (ORCPT ); Mon, 25 Jul 2022 21:47:49 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E4DCB28719 for ; Mon, 25 Jul 2022 18:47:48 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 7054DB81167 for ; Tue, 26 Jul 2022 01:47:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CCE4DC341C6; Tue, 26 Jul 2022 01:47:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1658800066; bh=cnZmXew4Y7QyRV3tolO7HHmTvcwRl8Oir8uQT46iIe0=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=YHDpbJ8EkU+wDp0GP9CeYk36bm41rG0TuuK56zn77kHUZ+fKOoM8fdfVlL/7z9Wqb u6CtvqsmQTfFxBVCm4XTwx4zxhPTosXX76cQ8kpZF4+Sp5s7yoezG/EiqljgIkkP8G kMebTqICsfCseD/g6S9z5rAFItoRaS2vr6eWdlENiqprFBnhhZ1q9sEYIUWSn+GKlp zdXxgv65wU539CSu7gEyLlPePXVb9cGr/aWh2neYzIAQmV+JMtwzNDRzHvTbjtipaH qtfqgt8w5BNCQDicJGvTxF4MUNLptof3e3+9M9igxLpyqls8JH2OULs4UCgIT/4hb4 qYJ6fOzL5UNkw== Date: Mon, 25 Jul 2022 18:47:44 -0700 From: Jakub Kicinski To: Jiri Pirko Cc: netdev@vger.kernel.org, davem@davemloft.net, idosch@nvidia.com, petrm@nvidia.com, pabeni@redhat.com, edumazet@google.com, mlxsw@nvidia.com, saeedm@nvidia.com, snelson@pensando.io Subject: Re: [patch net-next v4 01/12] net: devlink: make sure that devlink_try_get() works with valid pointer during xarray iteration Message-ID: <20220725184744.4e486fd6@kernel.org> In-Reply-To: <20220725082925.366455-2-jiri@resnulli.us> References: <20220725082925.366455-1-jiri@resnulli.us> <20220725082925.366455-2-jiri@resnulli.us> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, 25 Jul 2022 10:29:14 +0200 Jiri Pirko wrote: > From: Jiri Pirko > > Remove dependency on devlink_mutex during devlinks xarray iteration. > > The reason is that devlink_register/unregister() functions taking > devlink_mutex would deadlock during devlink reload operation of devlink > instance which registers/unregisters nested devlink instances. > > The devlinks xarray consistency is ensured internally by xarray. > There is a reference taken when working with devlink using > devlink_try_get(). But there is no guarantee that devlink pointer > picked during xarray iteration is not freed before devlink_try_get() > is called. > > Make sure that devlink_try_get() works with valid pointer. > Achieve it by: > 1) Splitting devlink_put() so the completion is sent only > after grace period. Completion unblocks the devlink_unregister() > routine, which is followed-up by devlink_free() > 2) During devlinks xa_array iteration, get devlink pointer from xa_array > holding RCU read lock and taking reference using devlink_try_get() > before unlock. > > Signed-off-by: Jiri Pirko Reviewed-by: Jakub Kicinski