From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757947Ab3KHRil (ORCPT ); Fri, 8 Nov 2013 12:38:41 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:45852 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757899Ab3KHRiX (ORCPT ); Fri, 8 Nov 2013 12:38:23 -0500 From: Konrad Rzeszutek Wilk To: Ian.Campbell@citrix.com, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, JBeulich@suse.com, david.vrabel@citrix.com, boris.ostrovsky@oracle.com Cc: Konrad Rzeszutek Wilk Subject: [PATCH 4/4] xen/xenbus: Avoid synchronous wait on XenBus stalling shutdown/restart. Date: Fri, 8 Nov 2013 12:38:06 -0500 Message-Id: <1383932286-25080-5-git-send-email-konrad.wilk@oracle.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1383932286-25080-1-git-send-email-konrad.wilk@oracle.com> References: <1383932286-25080-1-git-send-email-konrad.wilk@oracle.com> X-Source-IP: acsinet22.oracle.com [141.146.126.238] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The 'read_reply' works with 'process_msg' to read of a reply in XenBus. 'process_msg' is running from within the 'xenbus' thread. Whenever a message shows up in XenBus it is put on a xs_state.reply_list list and 'read_reply' picks it up. The problem is if the backend domain or the xenstored process is killed. In which case 'xenbus' is still awaiting - and 'read_reply' if called - stuck forever waiting for the reply_list to have some contents. This is normally not a problem - as the backend domain can come back or the xenstored process can be restarted. However if the domain is in process of being powered off/restarted/halted - there is no point of waiting on it coming back - as we are effectively being terminated and should not impede the progress. This patch solves this problem by checking the 'system_state' value to see if we are in heading towards death. We also make the wait mechanism a bit more asynchronous. Fixes-Bug: http://bugs.xenproject.org/xen/bug/8 Signed-off-by: Konrad Rzeszutek Wilk --- drivers/xen/xenbus/xenbus_xs.c | 24 +++++++++++++++++++++--- 1 file changed, 21 insertions(+), 3 deletions(-) diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c index b6d5fff..4f22706 100644 --- a/drivers/xen/xenbus/xenbus_xs.c +++ b/drivers/xen/xenbus/xenbus_xs.c @@ -148,9 +148,24 @@ static void *read_reply(enum xsd_sockmsg_type *type, unsigned int *len) while (list_empty(&xs_state.reply_list)) { spin_unlock(&xs_state.reply_lock); - /* XXX FIXME: Avoid synchronous wait for response here. */ - wait_event(xs_state.reply_waitq, - !list_empty(&xs_state.reply_list)); + wait_event_timeout(xs_state.reply_waitq, + !list_empty(&xs_state.reply_list), + msecs_to_jiffies(500)); + + /* + * If we are in the process of being shut-down there is + * no point of trying to contact XenBus - it is either + * killed (xenstored application) or the other domain + * has been killed or is unreachable. + */ + switch (system_state) { + case SYSTEM_POWER_OFF: + case SYSTEM_RESTART: + case SYSTEM_HALT: + return ERR_PTR(-EIO); + default: + break; + } spin_lock(&xs_state.reply_lock); } @@ -215,6 +230,9 @@ void *xenbus_dev_request_and_reply(struct xsd_sockmsg *msg) mutex_unlock(&xs_state.request_mutex); + if (IS_ERR(ret)) + return ret; + if ((msg->type == XS_TRANSACTION_END) || ((req_msg.type == XS_TRANSACTION_START) && (msg->type == XS_ERROR))) -- 1.8.3.1