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=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, 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 9F1CFC4CEC7 for ; Thu, 12 Sep 2019 17:48:00 +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 7733A20830 for ; Thu, 12 Sep 2019 17:47:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7733A20830 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]:37422 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i8TCI-0004Gs-Pr for qemu-devel@archiver.kernel.org; Thu, 12 Sep 2019 13:47:58 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:49153) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i8T9v-0002s0-Qa for qemu-devel@nongnu.org; Thu, 12 Sep 2019 13:45:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i8T9t-0006hr-0t for qemu-devel@nongnu.org; Thu, 12 Sep 2019 13:45:30 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33392) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i8T9s-0006h0-S5 for qemu-devel@nongnu.org; Thu, 12 Sep 2019 13:45:28 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 2394B8AC6FF for ; Thu, 12 Sep 2019 17:45:28 +0000 (UTC) Received: from work-vm (unknown [10.36.118.12]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E6DB95C22C; Thu, 12 Sep 2019 17:45:26 +0000 (UTC) Date: Thu, 12 Sep 2019 18:45:24 +0100 From: "Dr. David Alan Gilbert" To: Paolo Bonzini Message-ID: <20190912174524.GD2722@work-vm> References: <20190911190622.7629-1-dgilbert@redhat.com> <20190911190622.7629-2-dgilbert@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.69]); Thu, 12 Sep 2019 17:45:28 +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 v2 1/5] 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: , Cc: quintela@redhat.com, berrange@redhat.com, qemu-devel@nongnu.org, ehabkost@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Paolo Bonzini (pbonzini@redhat.com) wrote: > On 11/09/19 21:06, 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 infrastructure (and thus whatever the compiler's hooks are) to > > release it on all exits of the block. > > > > Signed-off-by: Dr. David Alan Gilbert > > --- > > include/qemu/rcu.h | 18 ++++++++++++++++++ > > 1 file changed, 18 insertions(+) > > > > diff --git a/include/qemu/rcu.h b/include/qemu/rcu.h > > index 22876d1428..8768a7b60a 100644 > > --- a/include/qemu/rcu.h > > +++ b/include/qemu/rcu.h > > @@ -154,6 +154,24 @@ extern void call_rcu1(struct rcu_head *head, RCUCBFunc *func); > > }), \ > > (RCUCBFunc *)g_free); > > > > +typedef void RCUReadAuto; > > +static inline RCUReadAuto *rcu_read_auto_lock(void) > > +{ > > + rcu_read_lock(); > > + /* Anything non-NULL causes the cleanup function to be called */ > > + return (void *)0x1; > > Doesn't this cause a warning (should be "(void *)(uintptr_t)1" instead)? Apparently not, but I'll change it anyway. > > +} > > + > > +static inline void rcu_read_auto_unlock(RCUReadAuto *r) > > +{ > > + rcu_read_unlock(); > > +} > > + > > +G_DEFINE_AUTOPTR_CLEANUP_FUNC(RCUReadAuto, rcu_read_auto_unlock) > > + > > +#define RCU_READ_LOCK_AUTO \ > > + g_autoptr(RCUReadAuto) _rcu_read_auto = rcu_read_auto_lock() > > + > > #ifdef __cplusplus > > } > > #endif > > > > Is it possible to make this a scope, like > > WITH_RCU_READ_LOCK() { > } > > ? Perhaps something like > > #define WITH_RCU_READ_LOCK() \ > WITH_RCU_READ_LOCK_(_rcu_read_auto##__COUNTER__) > > #define WITH_RCU_READ_LOCK_(var) \ > for (g_autoptr(RCUReadAuto) var = rcu_read_auto_lock(); > (var); rcu_read_auto_unlock(), (var) = NULL) > > where the dummy variable doubles as an execute-once guard and the gauto > cleanup is still used in case of a "break". I'm not sure if the above > raises a warning because of the variable declaration inside the for > loop, though. Yes, that works - I'm not seeing any warnings. Do you think it's best to use the block version for all cases or to use the non-block version by taste? The block version is quite nice, but that turns most of the patches into 'indent everything'. Dave > Thanks, > > Paolo -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK