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 X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 81166C433B4 for ; Fri, 7 May 2021 16:09:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 36E13613ED for ; Fri, 7 May 2021 16:09:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238064AbhEGQKp (ORCPT ); Fri, 7 May 2021 12:10:45 -0400 Received: from mail.kernel.org ([198.145.29.99]:36370 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235662AbhEGQKp (ORCPT ); Fri, 7 May 2021 12:10:45 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C4DDF61377; Fri, 7 May 2021 16:09:43 +0000 (UTC) Date: Fri, 7 May 2021 12:09:42 -0400 From: Steven Rostedt To: Stefano Garzarella Cc: LKML , Stefan Hajnoczi , "Michael S. Tsirkin" , Jason Wang , "David S. Miller" , Jakub Kicinski , kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, Joel Fernandes , Linux Trace Devel Subject: Re: [RFC][PATCH] vhost/vsock: Add vsock_list file to map cid with vhost tasks Message-ID: <20210507120942.0b06655e@gandalf.local.home> In-Reply-To: <20210507154332.hiblsd6ot5wzwkdj@steredhat> References: <20210505163855.32dad8e7@gandalf.local.home> <20210507141120.ot6xztl4h5zyav2c@steredhat> <20210507104036.711b0b10@gandalf.local.home> <20210507154332.hiblsd6ot5wzwkdj@steredhat> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; 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-trace-devel@vger.kernel.org On Fri, 7 May 2021 17:43:32 +0200 Stefano Garzarella wrote: > >The start/stop of a seq_file() is made for taking locks. I do this with all > >my code in ftrace. Yeah, there's a while loop between the two, but that's > >just to fill the buffer. It's not that long and it never goes to userspace > >between the two. You can even use this for spin locks (but I wouldn't > >recommend doing it for raw ones). > > Ah okay, thanks for the clarification! > > I was worried because building with `make C=2` I had these warnings: > > ../drivers/vhost/vsock.c:944:13: warning: context imbalance in 'vsock_start' - wrong count at exit > ../drivers/vhost/vsock.c:963:13: warning: context imbalance in 'vsock_stop' - unexpected unlock > > Maybe we need to annotate the functions somehow. Yep, I it should have been. static void *vsock_start(struct seq_file *m, loff_t *pos) __acquires(rcu) { [...] } static void vsock_stop(struct seq_file *m, void *p) __releases(rcu) { [...] } static int vsock_show(struct seq_file *m, void *v) __must_hold(rcu) { [...] } And guess what? I just copied those annotations from sock_hash_seq_start(), sock_hash_seq_show() and sock_hash_seq_stop() from net/core/sock_map.c which is doing exactly the same thing ;-) So there's definitely precedence for this. > > > > >> > >> >+ > >> >+ iter->index = -1; > >> >+ iter->node = NULL; > >> >+ t = vsock_next(m, iter, NULL); > >> >+ > >> >+ for (; iter->index < HASH_SIZE(vhost_vsock_hash) && l < *pos; > >> >+ t = vsock_next(m, iter, &l)) > >> >+ ; > >> > >> A while() maybe was more readable... > > > >Again, I just cut and pasted from my other code. > > > >If you have a good idea on how to implement this with netlink (something > >that ss or netstat can dislpay), I think that's the best way to go. > > Okay, I'll take a look and get back to you. > If it's too complicated, we can go ahead with this patch. Awesome, thanks! -- Steve