From patchwork Thu Nov 27 12:29:26 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 415485 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 5926414019D for ; Thu, 27 Nov 2014 23:34:49 +1100 (AEDT) Received: from localhost ([::1]:39129 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XtyHX-0003kG-ID for incoming@patchwork.ozlabs.org; Thu, 27 Nov 2014 07:34:47 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41540) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XtyCp-0005Xd-Ia for qemu-devel@nongnu.org; Thu, 27 Nov 2014 07:30:02 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XtyCj-0004FJ-DM for qemu-devel@nongnu.org; Thu, 27 Nov 2014 07:29:55 -0500 Received: from mx1.redhat.com ([209.132.183.28]:36775) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XtyCj-0004F4-6G for qemu-devel@nongnu.org; Thu, 27 Nov 2014 07:29:49 -0500 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 (8.14.4/8.14.4) with ESMTP id sARCTka2018142 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 27 Nov 2014 07:29:46 -0500 Received: from localhost (ovpn-112-66.ams2.redhat.com [10.36.112.66]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id sARCTjQ4024366; Thu, 27 Nov 2014 07:29:46 -0500 From: Stefan Hajnoczi To: Date: Thu, 27 Nov 2014 12:29:26 +0000 Message-Id: <1417091366-4469-7-git-send-email-stefanha@redhat.com> In-Reply-To: <1417091366-4469-1-git-send-email-stefanha@redhat.com> References: <1417091366-4469-1-git-send-email-stefanha@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: Peter Maydell , Paolo Bonzini , rth@redhat.com, Stefan Hajnoczi , Juan Quintela Subject: [Qemu-devel] [RFC 6/6] memory: make cpu_physical_memory_sync_dirty_bitmap() fully atomic 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 The fast path of cpu_physical_memory_sync_dirty_bitmap() directly manipulates the dirty bitmap. Use atomic_xchg() to make the test-and-clear atomic. Signed-off-by: Stefan Hajnoczi --- include/exec/ram_addr.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h index cdcbe9a..3d2a4c1 100644 --- a/include/exec/ram_addr.h +++ b/include/exec/ram_addr.h @@ -195,13 +195,13 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(unsigned long *dest, unsigned long *src = ram_list.dirty_memory[DIRTY_MEMORY_MIGRATION]; for (k = page; k < page + nr; k++) { - if (src[k]) { + unsigned long bits = atomic_xchg(&src[k], 0); + if (bits) { unsigned long new_dirty; new_dirty = ~dest[k]; - dest[k] |= src[k]; - new_dirty &= src[k]; + dest[k] |= bits; + new_dirty &= bits; num_dirty += ctpopl(new_dirty); - src[k] = 0; } } } else {