From nobody Wed Nov 12 05:23:18 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1568370506; cv=none; d=zoho.com; s=zohoarc; b=WVNS5NuZrSNSLsEsb9Fj4Q3T062axnI3L9dPB6cd3tSvfVN0vaPa+wBu8m1kfBgBopymCRbRnOpcYBRENITfqSz1kfUHuzVZA91ZPdEX2bFoxKCugPdBmkFA+T2zYuCaTc+oPe8udvsu9N+A+E8Ci78YwRDKGUvAkqrUHeNm55M= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zoho.com; s=zohoarc; t=1568370506; h=Content-Transfer-Encoding:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To:ARC-Authentication-Results; bh=94eIFaCpZK6lhFHRuS2i2ttcIyMV7RoFUocJIDhL/BI=; b=ofHhevewezYZdj9p5LoT15iCvx92vzUeq5feOkJcxyAl3Uk6TgLczxsOTao60YP8Hxsbb5D9n0++kco3Jnh+kxh19FJMV7KvD6VeJ8TbJuzfmvP/Z8XEl0TrScqfCgOuRCREPQ7uYI8DGb9u3pPrlRIhcmmbBRF9ForjwTQp/s0= ARC-Authentication-Results: i=1; mx.zoho.com; spf=pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail header.from= (p=none dis=none) header.from= Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1568370506718268.97981253799344; Fri, 13 Sep 2019 03:28:26 -0700 (PDT) Received: from localhost ([::1]:42158 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i8ioK-0001a8-35 for importer@patchew.org; Fri, 13 Sep 2019 06:28:16 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:35165) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i8ilt-00085D-HD for qemu-devel@nongnu.org; Fri, 13 Sep 2019 06:25:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i8ils-0005oU-Ay for qemu-devel@nongnu.org; Fri, 13 Sep 2019 06:25:45 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50626) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i8ils-0005nn-2i for qemu-devel@nongnu.org; Fri, 13 Sep 2019 06:25:44 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6DFF381DE7 for ; Fri, 13 Sep 2019 10:25:43 +0000 (UTC) Received: from dgilbert-t580.localhost (unknown [10.36.118.12]) by smtp.corp.redhat.com (Postfix) with ESMTP id 448645D9E1; Fri, 13 Sep 2019 10:25:42 +0000 (UTC) From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org, pbonzini@redhat.com, ehabkost@redhat.com, berrange@redhat.com, quintela@redhat.com Date: Fri, 13 Sep 2019 11:25:34 +0100 Message-Id: <20190913102538.24167-2-dgilbert@redhat.com> In-Reply-To: <20190913102538.24167-1-dgilbert@redhat.com> References: <20190913102538.24167-1-dgilbert@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Fri, 13 Sep 2019 10:25:43 +0000 (UTC) Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH v3 1/5] rcu: Add automatically released rcu_read_lock variants 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: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Content-Type: text/plain; charset="utf-8" From: "Dr. David Alan Gilbert" RCU_READ_LOCK_GUARD() 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. WITH_RCU_READ_LOCK_GUARD() is similar but is used as a wrapper for the lock, i.e.: WITH_RCU_READ_LOCK_GUARD() { stuff under lock } Signed-off-by: Dr. David Alan Gilbert Acked-by: Paolo Bonzini Reviewed-by: Daniel P. Berrang=C3=A9 --- docs/devel/rcu.txt | 16 ++++++++++++++++ include/qemu/rcu.h | 25 +++++++++++++++++++++++++ 2 files changed, 41 insertions(+) diff --git a/docs/devel/rcu.txt b/docs/devel/rcu.txt index c84e7f42b2..d83fed2f79 100644 --- a/docs/devel/rcu.txt +++ b/docs/devel/rcu.txt @@ -187,6 +187,22 @@ The following APIs must be used before RCU is used in = a thread: Note that these APIs are relatively heavyweight, and should _not_ be nested. =20 +Convenience macros +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +Two macros are provided that automatically release the read lock at the +end of the scope. + + RCU_READ_LOCK_GUARD() + + Takes the lock and will release it at the end of the block it's + used in. + + WITH_RCU_READ_LOCK_GUARD() { code } + + Is used at the head of a block to protect the code within the blo= ck. + +Note that 'goto'ing out of the guarded block will also drop the lock. =20 DIFFERENCES WITH LINUX =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D diff --git a/include/qemu/rcu.h b/include/qemu/rcu.h index 22876d1428..3a8d4cf28b 100644 --- a/include/qemu/rcu.h +++ b/include/qemu/rcu.h @@ -154,6 +154,31 @@ extern void call_rcu1(struct rcu_head *head, RCUCBFunc= *func); }), \ (RCUCBFunc *)g_free); =20 +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 *)(uintptr_t)0x1; +} + +static inline void rcu_read_auto_unlock(RCUReadAuto *r) +{ + rcu_read_unlock(); +} + +G_DEFINE_AUTOPTR_CLEANUP_FUNC(RCUReadAuto, rcu_read_auto_unlock) + +#define WITH_RCU_READ_LOCK_GUARD() \ + WITH_RCU_READ_LOCK_GUARD_(_rcu_read_auto##__COUNTER__) + +#define WITH_RCU_READ_LOCK_GUARD_(var) \ + for (g_autoptr(RCUReadAuto) var =3D rcu_read_auto_lock(); \ + (var); rcu_read_auto_unlock(var), (var) =3D NULL) + +#define RCU_READ_LOCK_GUARD() \ + g_autoptr(RCUReadAuto) _rcu_read_auto =3D rcu_read_auto_lock() + #ifdef __cplusplus } #endif --=20 2.21.0