From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sunil Mushran <sunil.mushran@oracle.com>
Date: Tue, 30 Nov 2010 21:33:32 -0800
Subject: [Ocfs2-devel] [PATCH] ocfs2/dlm: queue ast in lockres->spinlock
In-Reply-To: <20101201025218.GA3709@laptop.jp.oracle.com>
References: <201011301551.oAUD3n5c002863@rcsinet13.oracle.com>
	<4CF54F55.8080007@oracle.com>
	<20101201025218.GA3709@laptop.jp.oracle.com>
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To: ocfs2-devel@oss.oracle.com

On 11/30/2010 06:52 PM, Wengang Wang wrote:
> First I have to say that the scenario is in my thought only, no tcpdump
> shows that. Only the node C wanting a PR is the truth from the vmcore.
>
> Let's consider this situation:
>
> The create lock(CL) is for a PR;
> the up convert(UC) is PR->EX;
> there is an existing PR granted for another node(say node D) before the UC comes
>
> The UC comes. Because of the existing PR, the UC lock is moved to converting list.
> dlm_thread takes care it later.
> The CL comes. no conflict found(see dlm_can_grant_new_lock, convert_type not
> checked there). so it's not added to blocked list.
>
> Seems the above scenario can trigger a BAST before AST.

dlm_can_grant_new_lock() should be looking at convert_type also and
add the lock to the blocked list in this case.

This is not just to plug this hole but is as per the spec.