Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752461AbaAZDov (ORCPT ); Sat, 25 Jan 2014 22:44:51 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:22593 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752104AbaAZDou convert rfc822-to-8bit (ORCPT ); Sat, 25 Jan 2014 22:44:50 -0500 User-Agent: K-9 Mail for Android In-Reply-To: References: <1383932286-25080-1-git-send-email-konrad.wilk@oracle.com> <1383932286-25080-5-git-send-email-konrad.wilk@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Subject: RE: [Xen-devel] [PATCH 4/4] xen/xenbus: Avoid synchronous wait on XenBus stalling shutdown/restart. From: Konrad Rzeszutek Wilk Date: Sat, 25 Jan 2014 22:44:21 -0500 To: "Zhang, Yang Z" , "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" Message-ID: 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 "Zhang, Yang Z" wrote: >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. > No. It needs rework. >> 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/