From patchwork Fri Jan 30 15:19:53 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paolo Bonzini X-Patchwork-Id: 434942 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 D3176140140 for ; Sat, 31 Jan 2015 02:23:12 +1100 (AEDT) Received: from localhost ([::1]:37305 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YHDPb-0002vF-1I for incoming@patchwork.ozlabs.org; Fri, 30 Jan 2015 10:23:11 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59373) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YHDMn-0006Zk-5Z for qemu-devel@nongnu.org; Fri, 30 Jan 2015 10:20:18 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YHDMm-0005Da-B3 for qemu-devel@nongnu.org; Fri, 30 Jan 2015 10:20:17 -0500 Received: from mail-wg0-x22c.google.com ([2a00:1450:400c:c00::22c]:37276) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YHDMm-0005DN-4r for qemu-devel@nongnu.org; Fri, 30 Jan 2015 10:20:16 -0500 Received: by mail-wg0-f44.google.com with SMTP id z12so27522619wgg.3 for ; Fri, 30 Jan 2015 07:20:15 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:from:to:subject:date:message-id:in-reply-to:references; bh=U/wnLjUQP2Sbw/2RWBIRp7CLVgYOrSFWCsGVq+/fUds=; b=tJuOAMh0dRrMD0PMdVv6pVj2QC7VsZjl1dvB4CPdqZLQg71zcgvvY+lOpwsxvkhc7a lz1jlZ0L7pHekCEkcbjg18znqZWjsIajYdlsRVs8rSNEVw8xsZCWvjDzvHIkNV8Nudxg 0mpqZIt3ppj9BPowlJ6FK3UaygCmFIrcwP2/Oiy1Wkuv3NwBpdHk+RQ2hpM/G0OAOkyR fou8if+KL95wh6AIuk328uyf39qFSI2rDojwC98elAlbWjRwEJyVegTHt2/S6La+5xju 7GPh8VBVfW83GGulOZofbPJbs8/5W/u7ClUoGtSpAkm6V1LHVSWBgjsS8xlgAfBO+kMH TKWA== X-Received: by 10.194.239.233 with SMTP id vv9mr13055017wjc.90.1422631215576; Fri, 30 Jan 2015 07:20:15 -0800 (PST) Received: from playground.station (net-93-66-105-136.cust.vodafonedsl.it. [93.66.105.136]) by mx.google.com with ESMTPSA id n6sm15341184wjy.8.2015.01.30.07.20.13 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 30 Jan 2015 07:20:14 -0800 (PST) From: Paolo Bonzini To: qemu-devel@nongnu.org Date: Fri, 30 Jan 2015 16:19:53 +0100 Message-Id: <1422631197-26063-8-git-send-email-pbonzini@redhat.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1422631197-26063-1-git-send-email-pbonzini@redhat.com> References: <1422631197-26063-1-git-send-email-pbonzini@redhat.com> X-detected-operating-system: by eggs.gnu.org: Error: Malformed IPv6 address (bad octet value). X-Received-From: 2a00:1450:400c:c00::22c Subject: [Qemu-devel] [PULL 07/11] memory: avoid ref/unref in memory_region_find 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 Do the entire lookup under RCU, which avoids atomic operations in flatview_ref and flatview_unref. Reviewed-by: Fam Zheng Signed-off-by: Paolo Bonzini --- memory.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/memory.c b/memory.c index a844ced..9b91243 100644 --- a/memory.c +++ b/memory.c @@ -1828,11 +1828,11 @@ MemoryRegionSection memory_region_find(MemoryRegion *mr, } range = addrrange_make(int128_make64(addr), int128_make64(size)); - view = address_space_get_flatview(as); + rcu_read_lock(); + view = atomic_rcu_read(&as->current_map); fr = flatview_lookup(view, range); if (!fr) { - flatview_unref(view); - return ret; + goto out; } while (fr > view->ranges && addrrange_intersects(fr[-1].addr, range)) { @@ -1849,8 +1849,8 @@ MemoryRegionSection memory_region_find(MemoryRegion *mr, ret.offset_within_address_space = int128_get64(range.start); ret.readonly = fr->readonly; memory_region_ref(ret.mr); - - flatview_unref(view); +out: + rcu_read_unlock(); return ret; }