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 606A8C433FE for ; Tue, 19 Oct 2021 16:53:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4C17E6113B for ; Tue, 19 Oct 2021 16:53:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234570AbhJSQ4E (ORCPT ); Tue, 19 Oct 2021 12:56:04 -0400 Received: from mga12.intel.com ([192.55.52.136]:45765 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234509AbhJSQ4D (ORCPT ); Tue, 19 Oct 2021 12:56:03 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10142"; a="208675114" X-IronPort-AV: E=Sophos;i="5.87,164,1631602800"; d="scan'208";a="208675114" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Oct 2021 09:53:44 -0700 X-IronPort-AV: E=Sophos;i="5.87,164,1631602800"; d="scan'208";a="462833841" Received: from jacob-builder.jf.intel.com (HELO jacob-builder) ([10.7.199.155]) by orsmga002-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Oct 2021 09:53:43 -0700 Date: Tue, 19 Oct 2021 09:57:34 -0700 From: Jacob Pan To: Jason Gunthorpe Cc: "Liu, Yi L" , "alex.williamson@redhat.com" , "hch@lst.de" , "jasowang@redhat.com" , "joro@8bytes.org" , "jean-philippe@linaro.org" , "Tian, Kevin" , "parav@mellanox.com" , "lkml@metux.net" , "pbonzini@redhat.com" , "lushenming@huawei.com" , "eric.auger@redhat.com" , "corbet@lwn.net" , "Raj, Ashok" , "yi.l.liu@linux.intel.com" , "Tian, Jun J" , "Wu, Hao" , "Jiang, Dave" , "kwankhede@nvidia.com" , "robin.murphy@arm.com" , "kvm@vger.kernel.org" , "iommu@lists.linux-foundation.org" , "dwmw2@infradead.org" , "linux-kernel@vger.kernel.org" , "baolu.lu@linux.intel.com" , "david@gibson.dropbear.id.au" , "nicolinc@nvidia.com" , jacob.jun.pan@linux.intel.com Subject: Re: [RFC 01/20] iommu/iommufd: Add /dev/iommu core Message-ID: <20211019095734.2a3fb785@jacob-builder> In-Reply-To: <20211015111807.GD2744544@nvidia.com> References: <20210919063848.1476776-1-yi.l.liu@intel.com> <20210919063848.1476776-2-yi.l.liu@intel.com> <20210921154138.GM327412@nvidia.com> <20211015111807.GD2744544@nvidia.com> Organization: OTC X-Mailer: Claws Mail 3.17.5 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jason, On Fri, 15 Oct 2021 08:18:07 -0300, Jason Gunthorpe wrote: > On Fri, Oct 15, 2021 at 09:18:06AM +0000, Liu, Yi L wrote: > > > > Acquire from the xarray is > > > rcu_lock() > > > ioas = xa_load() > > > if (ioas) > > > if (down_read_trylock(&ioas->destroying_lock)) > > > > all good suggestions, will refine accordingly. Here destroying_lock is a > > rw_semaphore. right? Since down_read_trylock() accepts a rwsem. > > Yes, you probably need a sleeping lock > I am not following why we want a sleeping lock inside RCU protected section? For ioas, do we really care about the stale data to choose rw_lock vs RCU? Destroying can be kfree_rcu? > Jason Thanks, Jacob