Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932713AbaFCOUi (ORCPT ); Tue, 3 Jun 2014 10:20:38 -0400 Received: from mx1.redhat.com ([209.132.183.28]:64777 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752926AbaFCOUg (ORCPT ); Tue, 3 Jun 2014 10:20:36 -0400 Message-ID: <538DD9AC.8050606@redhat.com> Date: Tue, 03 Jun 2014 16:20:28 +0200 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Eric Dumazet CC: "Michael S. Tsirkin" , netdev@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, David Miller Subject: Re: [PULL 2/2] vhost: replace rcu with mutex References: <1401744482-17764-1-git-send-email-mst@redhat.com> <1401744482-17764-3-git-send-email-mst@redhat.com> <1401746280.3645.187.camel@edumazet-glaptop2.roam.corp.google.com> <538DC422.1050303@redhat.com> <1401803863.3645.208.camel@edumazet-glaptop2.roam.corp.google.com> In-Reply-To: <1401803863.3645.208.camel@edumazet-glaptop2.roam.corp.google.com> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Il 03/06/2014 15:57, Eric Dumazet ha scritto: > On Tue, 2014-06-03 at 14:48 +0200, Paolo Bonzini wrote: >> Il 02/06/2014 23:58, Eric Dumazet ha scritto: >>> This looks dubious >>> >>> What about using kfree_rcu() instead ? >> >> It would lead to unbound allocation from userspace. > > Look at how we did this in commit > c3059477fce2d956a0bb3e04357324780c5d8eeb That would make VHOST_SET_MEMORY as slow as before (even though once every few times). >>> translate_desc() still uses rcu_read_lock(), its not clear if the mutex >>> is really held. >> >> Yes, vhost_get_vq_desc must be called with the vq mutex held. >> >> The rcu_read_lock/unlock in translate_desc is unnecessary. > > Yep, this is what I pointed out. This is not only necessary, but > confusing and might be incorrectly copy/pasted in the future. > > This patch is a partial one and leaves confusion. I agree. Paolo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/