From: Wang Chen Subject: Re: [PATCH] nfs lockd: detect grace_list corruption Date: Wed, 06 May 2009 17:17:20 +0800 Message-ID: <4A0155A0.4020008@cn.fujitsu.com> References: <49F12D78.2040304@cn.fujitsu.com> <20090424231252.GD22477@fieldses.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Cc: neilb@suse.de, Trond.Myklebust@netapp.com, linux-nfs@vger.kernel.org, FNST-Bian Naimeng To: "J. Bruce Fields" Return-path: Received: from cn.fujitsu.com ([222.73.24.84]:49153 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1753111AbZEFJR6 (ORCPT ); Wed, 6 May 2009 05:17:58 -0400 In-Reply-To: <20090424231252.GD22477@fieldses.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: J. Bruce Fields said the following on 2009-4-25 7:12: > On Fri, Apr 24, 2009 at 11:09:44AM +0800, Wang Chen wrote: >> Although I can't reproduce it now, it really happened that some lock manager >> started grace period but didn't end it. >> This causes an lm entry be left in grace_list, and when service nfs restart, >> the same lm will be added again into the list. >> As you know, adding an entry, which is in the list, to a list will leads to >> list corruption. > > I'd really like to understand why locks_end_grace() isn't being called. > I'm probably overlooking something obvious, but I just can't see how > lockd or nfsd can be shut down right now without locks_end_grace() being > called. > Me neither can figure out why locks_end_grace() isn't being called. But do locks_start_grace() twice can trigger this warning too. You can do 1. service nfs restart 2. (immediately) kill -s SIGKILL lockd this can trigger --- lockd(void *vrqstp) ... if (signalled()) { flush_signals(current); if (nlmsvc_ops) { nlmsvc_invalidate_all(); set_grace_period(); --- and makes locks_start_grace() be called twice without locks_end_grace(). So I still suggest to do something to protect the lm list. :)