Date: Wed, 24 Nov 2004 17:05:53 -0800
From: Andrew Morton <akpm@osdl.org>
To: Neil Brown <neilb@cse.unsw.edu.au>
Cc: phil@dier.us, axboe@suse.de, linux-kernel@vger.kernel.org
Subject: Re: oops with dual xeon 2.8ghz  4gb ram +smp, software raid, lvm,
 and xfs
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Neil Brown <neilb@cse.unsw.edu.au> wrote:
>
> If a ->make_request_fn did synchronous IO things would definitely get
>  unstuck.   But I don't think they should and doubt if they do (md
>  certainly doesn't).

generic_make_request() can block in get_request_wait(), but I can't
immediately think of a way in which that can deadlock things, especially if
each level is using a distinct queue.

It could certainly deadlock if a higher-level make_request() caller
required allocation of two or more requests at a lower level - all we'd
need is N/2 proceses each trying to allocate two requests.  But such a
lockup could happen in the current code anyway..  
-
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