From patchwork Thu Jan 24 07:48:25 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Denis Plotnikov X-Patchwork-Id: 10778469 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 326E791E for ; Thu, 24 Jan 2019 07:54:32 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2723D2C37D for ; Thu, 24 Jan 2019 07:54:32 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 1AB472C39B; Thu, 24 Jan 2019 07:54:32 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id EE6192C37D for ; Thu, 24 Jan 2019 07:54:30 +0000 (UTC) Received: from localhost ([127.0.0.1]:49211 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gmZqH-00012e-Sq for patchwork-qemu-devel@patchwork.kernel.org; Thu, 24 Jan 2019 02:54:29 -0500 Received: from eggs.gnu.org ([209.51.188.92]:39071) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gmZpc-0000Zf-0P for qemu-devel@nongnu.org; Thu, 24 Jan 2019 02:53:48 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gmZpa-0004LT-VK for qemu-devel@nongnu.org; Thu, 24 Jan 2019 02:53:47 -0500 Received: from relay.sw.ru ([185.231.240.75]:55018) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gmZkc-0008GX-Nb; Thu, 24 Jan 2019 02:48:39 -0500 Received: from [10.94.4.71] (helo=dptest2.qa.sw.ru) by relay.sw.ru with esmtp (Exim 4.91) (envelope-from ) id 1gmZkW-0006Ga-DP; Thu, 24 Jan 2019 10:48:32 +0300 From: Denis Plotnikov To: mreitz@redhat.com, kwolf@redhat.com Date: Thu, 24 Jan 2019 10:48:25 +0300 Message-Id: <20190124074825.2327-1-dplotnikov@virtuozzo.com> X-Mailer: git-send-email 2.17.0 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 185.231.240.75 Subject: [Qemu-devel] [PATCH] block: skip initializer BDS on recursive aio context attachment/detachment X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: vsementsov@virtuozzo.com, qemu-devel@nongnu.org, qemu-block@nongnu.org, den@virtuozzo.com Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP When there is a Backup Block Job running and shutdown command is sent to a guest, the guest crushes due to assert(!bs->walking_aio_notifiers). Call stack: 0 __GI_raise 1 __GI_abort 2 __assert_fail_base 3 __GI___assert_fail 4 bdrv_detach_aio_context (bs=0x55f54d65c000) <<< 5 bdrv_detach_aio_context (bs=0x55f54fc8a800) 6 bdrv_set_aio_context (bs=0x55f54fc8a800, ...) 7 block_job_attached_aio_context 8 bdrv_attach_aio_context (bs=0x55f54d65c000, ...) <<< 9 bdrv_set_aio_context (bs=0x55f54d65c000) 10 blk_set_aio_context 11 virtio_blk_data_plane_stop 12 virtio_bus_stop_ioeventfd 13 virtio_vmstate_change 14 vm_state_notify (running=0, state=RUN_STATE_SHUTDOWN) 15 do_vm_stop (state=RUN_STATE_SHUTDOWN, send_stop=true) 16 vm_stop (state=RUN_STATE_SHUTDOWN) 17 main_loop_should_exit 18 main_loop 19 main This happens because of "new" context attachment to VM disk bds. When attaching a new context the corresponding aio context handler is called for each of aio_notifiers registered on the VM disk bds context. Among those handlers there is the block_job_attached_aio_context handler which sets a new aio context for the block job bds. When doing so, the old context is detached from all the block job bds children and one of them is the VM disk bds, serving as backing store for the blockjob bds, although the VM disk bds is actually the initializer of that process. Since the VM disk bds is protected with walking_aio_notifiers flag from double processing in recursive calls, the assert fires. The patch fixes the problem by skipping the bds-es in recursive calls which have started attachment/detachment already. Signed-off-by: Denis Plotnikov --- block.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/block.c b/block.c index 9b1c5c5eaf..35a19fe1df 100644 --- a/block.c +++ b/block.c @@ -5064,7 +5064,9 @@ void bdrv_detach_aio_context(BlockDriverState *bs) bs->drv->bdrv_detach_aio_context(bs); } QLIST_FOREACH(child, &bs->children, next) { - bdrv_detach_aio_context(child->bs); + if (!child->bs->walking_aio_notifiers) { + bdrv_detach_aio_context(child->bs); + } } bs->aio_context = NULL; @@ -5083,7 +5085,9 @@ void bdrv_attach_aio_context(BlockDriverState *bs, bs->aio_context = new_context; QLIST_FOREACH(child, &bs->children, next) { - bdrv_attach_aio_context(child->bs, new_context); + if (!child->bs->walking_aio_notifiers) { + bdrv_attach_aio_context(child->bs, new_context); + } } if (bs->drv->bdrv_attach_aio_context) { bs->drv->bdrv_attach_aio_context(bs, new_context);