From patchwork Thu Aug 6 13:36:13 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paolo Bonzini X-Patchwork-Id: 504712 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 7C0121402B7 for ; Fri, 7 Aug 2015 00:10:26 +1000 (AEST) Received: from localhost ([::1]:45330 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZNLsG-0007bc-CW for incoming@patchwork.ozlabs.org; Thu, 06 Aug 2015 10:10:24 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41051) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZNLo6-0005RS-CF for qemu-devel@nongnu.org; Thu, 06 Aug 2015 10:06:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZNLo1-0000cc-B1 for qemu-devel@nongnu.org; Thu, 06 Aug 2015 10:06:06 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33526) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZNLnp-0000YA-5Q; Thu, 06 Aug 2015 10:05:49 -0400 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (Postfix) with ESMTPS id D8B2D98C34; Thu, 6 Aug 2015 14:05:48 +0000 (UTC) Received: from donizetti.redhat.com (ovpn-112-80.ams2.redhat.com [10.36.112.80]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t76DaI9U016488; Thu, 6 Aug 2015 09:37:58 -0400 From: Paolo Bonzini To: qemu-devel@nongnu.org Date: Thu, 6 Aug 2015 15:36:13 +0200 Message-Id: <1438868176-20364-16-git-send-email-pbonzini@redhat.com> In-Reply-To: <1438868176-20364-1-git-send-email-pbonzini@redhat.com> References: <1438868176-20364-1-git-send-email-pbonzini@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.23 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: kwolf@redhat.com, famz@redhat.com, stefanha@redhat.com, qemu-block@nongnu.org Subject: [Qemu-devel] [PATCH 15/18] quorum: use atomics for rewrite_count X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org This is simpler than taking and releasing the AioContext lock. Both quorum_rewrite_aio_cb and quorum_aio_finalize will be called without any lock taken. Signed-off-by: Paolo Bonzini --- block/quorum.c | 11 +++-------- 1 file changed, 3 insertions(+), 8 deletions(-) diff --git a/block/quorum.c b/block/quorum.c index 4e66221..0a42962 100644 --- a/block/quorum.c +++ b/block/quorum.c @@ -250,15 +250,10 @@ static void quorum_rewrite_aio_cb(void *opaque, int ret) { QuorumAIOCB *acb = opaque; - /* one less rewrite to do */ - acb->rewrite_count--; - /* wait until all rewrite callbacks have completed */ - if (acb->rewrite_count) { - return; + if (atomic_fetch_dec(&acb->rewrite_count) == 1) { + quorum_aio_finalize(acb); } - - quorum_aio_finalize(acb); } static BlockAIOCB *read_fifo_child(QuorumAIOCB *acb); @@ -361,7 +356,7 @@ static bool quorum_rewrite_bad_versions(BDRVQuorumState *s, QuorumAIOCB *acb, } /* quorum_rewrite_aio_cb will count down this to zero */ - acb->rewrite_count = count; + atomic_mb_set(&acb->rewrite_count, count); /* now fire the correcting rewrites */ QLIST_FOREACH(version, &acb->votes.vote_list, next) {