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=-8.5 required=3.0 tests=FROM_EXCESS_BASE64, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 C68E0C5ACAE for ; Wed, 11 Sep 2019 16:57:14 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A0F3C20872 for ; Wed, 11 Sep 2019 16:57:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A0F3C20872 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:53914 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i85vd-0005jX-S8 for qemu-devel@archiver.kernel.org; Wed, 11 Sep 2019 12:57:13 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:44839) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i85uz-0004um-Vs for qemu-devel@nongnu.org; Wed, 11 Sep 2019 12:56:35 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i85ux-0008Le-Ox for qemu-devel@nongnu.org; Wed, 11 Sep 2019 12:56:32 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53976) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i85ux-0008L9-Jw for qemu-devel@nongnu.org; Wed, 11 Sep 2019 12:56:31 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6960BC08C33F for ; Wed, 11 Sep 2019 16:56:30 +0000 (UTC) Received: from redhat.com (unknown [10.42.17.64]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 93B9C19C6A; Wed, 11 Sep 2019 16:56:29 +0000 (UTC) Date: Wed, 11 Sep 2019 17:56:27 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: "Dr. David Alan Gilbert (git)" Message-ID: <20190911165627.GG24295@redhat.com> References: <20190911164202.31136-1-dgilbert@redhat.com> <20190911164202.31136-2-dgilbert@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190911164202.31136-2-dgilbert@redhat.com> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Wed, 11 Sep 2019 16:56:30 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH 1/3] rcu: Add automatically released rcu_read_lock variant X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: pbonzini@redhat.com, qemu-devel@nongnu.org, quintela@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Sep 11, 2019 at 05:42:00PM +0100, Dr. David Alan Gilbert (git) wrote: > From: "Dr. David Alan Gilbert" > > RCU_READ_LOCK_AUTO takes the rcu_read_lock and then uses glib's > g_auto infrastrcture (and thus whatever the compilers hooks are) to > release it on all exits of the block. > > Note this macro has a variable declaration in, and hence is not in > a while loop. > > Signed-off-by: Dr. David Alan Gilbert > --- > include/qemu/rcu.h | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/include/qemu/rcu.h b/include/qemu/rcu.h > index 22876d1428..6a25b27d28 100644 > --- a/include/qemu/rcu.h > +++ b/include/qemu/rcu.h > @@ -154,6 +154,18 @@ extern void call_rcu1(struct rcu_head *head, RCUCBFunc *func); > }), \ > (RCUCBFunc *)g_free); > > +typedef char rcu_read_auto_t; > +static inline void rcu_read_auto_unlock(rcu_read_auto_t *r) > +{ > + rcu_read_unlock(); > +} > + > +G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC(rcu_read_auto_t, rcu_read_auto_unlock) > > +#define RCU_READ_LOCK_AUTO g_auto(rcu_read_auto_t) \ > + _rcu_read_auto = 'x'; \ > + rcu_read_lock(); > + Functionally this works, but my gut feeling would be to follow the design of GMutexLocker as-is: https://developer.gnome.org/glib/stable/glib-Threads.html#g-mutex-locker-new so you get a use pattern of g_autoptr(rcu_read_locker) locker = rcu_read_locker_new(); This makes it explicit that the code is creating a variable here, which in turns means it is clear to force unlock early with g_clear_pointer(&locker, rcu_read_locker_free) Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|