Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752198AbaAZBOL (ORCPT ); Sat, 25 Jan 2014 20:14:11 -0500 Received: from mga01.intel.com ([192.55.52.88]:51998 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750840AbaAZBOJ convert rfc822-to-8bit (ORCPT ); Sat, 25 Jan 2014 20:14:09 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.95,721,1384329600"; d="scan'208";a="470826735" From: "Zhang, Yang Z" To: Konrad Rzeszutek Wilk , "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" Subject: RE: [Xen-devel] [PATCH 4/4] xen/xenbus: Avoid synchronous wait on XenBus stalling shutdown/restart. Thread-Topic: [Xen-devel] [PATCH 4/4] xen/xenbus: Avoid synchronous wait on XenBus stalling shutdown/restart. Thread-Index: AQHO3KmE8nzOae4vI0ON33E2bX7xXpqWrgxw Date: Sun, 26 Jan 2014 01:13:51 +0000 Message-ID: References: <1383932286-25080-1-git-send-email-konrad.wilk@oracle.com> <1383932286-25080-5-git-send-email-konrad.wilk@oracle.com> In-Reply-To: <1383932286-25080-5-git-send-email-konrad.wilk@oracle.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.239.127.40] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Konrad Rzeszutek Wilk wrote on 2013-11-09: > 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. > Hi, Konrad, Is this patch applied in Linux upstream tree? I didn't find it with latest Linux upstream source. > 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))) Best regards, Yang -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/