From patchwork Thu Apr 11 15:44:33 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 235858 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 5C49F2C00C8 for ; Fri, 12 Apr 2013 04:06:07 +1000 (EST) Received: from localhost ([::1]:42078 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UQJis-0005zx-NO for incoming@patchwork.ozlabs.org; Thu, 11 Apr 2013 11:47:38 -0400 Received: from eggs.gnu.org ([208.118.235.92]:36065) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UQJiN-0005tE-Kh for qemu-devel@nongnu.org; Thu, 11 Apr 2013 11:47:10 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UQJiH-0003CX-9X for qemu-devel@nongnu.org; Thu, 11 Apr 2013 11:47:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39778) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UQJiH-0003Bz-0m for qemu-devel@nongnu.org; Thu, 11 Apr 2013 11:47:01 -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 (8.14.4/8.14.4) with ESMTP id r3BFinDQ003440 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Thu, 11 Apr 2013 11:44:49 -0400 Received: from localhost (ovpn-112-31.ams2.redhat.com [10.36.112.31]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id r3BFilYP006451; Thu, 11 Apr 2013 11:44:48 -0400 From: Stefan Hajnoczi To: Date: Thu, 11 Apr 2013 17:44:33 +0200 Message-Id: <1365695085-27970-2-git-send-email-stefanha@redhat.com> In-Reply-To: <1365695085-27970-1-git-send-email-stefanha@redhat.com> References: <1365695085-27970-1-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: Kevin Wolf , Paolo Bonzini , Anthony Liguori , pingfank@linux.vnet.ibm.com Subject: [Qemu-devel] [RFC 01/13] block: stop relying on io_flush() in bdrv_drain_all() 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 If a block driver has no file descriptors to monitor but there are still active requests, it can return 1 from .io_flush(). This is used to spin during synchronous I/O. Stop relying on .io_flush() and instead check QLIST_EMPTY(&bs->tracked_requests) to decide whether there are active requests. This is the first step in removing .io_flush() so that event loops no longer need to have the concept of synchronous I/O. Eventually we may be able to kill synchronous I/O completely by running everything in a coroutine, but that is future work. Signed-off-by: Stefan Hajnoczi --- block.c | 28 ++++++++++++++++++---------- 1 file changed, 18 insertions(+), 10 deletions(-) diff --git a/block.c b/block.c index 602d8a4..93d676b 100644 --- a/block.c +++ b/block.c @@ -1360,6 +1360,22 @@ void bdrv_close_all(void) } } +/* Check if any requests are in-flight (including throttled requests) */ +static bool bdrv_requests_pending(void) +{ + BlockDriverState *bs; + + QTAILQ_FOREACH(bs, &bdrv_states, list) { + if (!QLIST_EMPTY(&bs->tracked_requests)) { + return true; + } + if (!qemu_co_queue_empty(&bs->throttled_reqs)) { + return true; + } + } + return false; +} + /* * Wait for pending requests to complete across all BlockDriverStates * @@ -1375,26 +1391,18 @@ void bdrv_close_all(void) void bdrv_drain_all(void) { BlockDriverState *bs; - bool busy; - - do { - busy = qemu_aio_wait(); + while (bdrv_requests_pending()) { /* FIXME: We do not have timer support here, so this is effectively * a busy wait. */ QTAILQ_FOREACH(bs, &bdrv_states, list) { if (!qemu_co_queue_empty(&bs->throttled_reqs)) { qemu_co_queue_restart_all(&bs->throttled_reqs); - busy = true; } } - } while (busy); - /* If requests are still pending there is a bug somewhere */ - QTAILQ_FOREACH(bs, &bdrv_states, list) { - assert(QLIST_EMPTY(&bs->tracked_requests)); - assert(qemu_co_queue_empty(&bs->throttled_reqs)); + qemu_aio_wait(); } }