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Date: Mon, 2 Apr 2007 17:40:33 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: "kalash nainwal" <kalash.nainwal@gmail.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] (re)register_binfmt returns with -EBUSY
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On Mon, 2 Apr 2007 18:24:15 +0530
"kalash nainwal" <kalash.nainwal@gmail.com> wrote:

> When a binary format is unregistered and re-registered,
> register_binfmt fails with -EBUSY. The reason is that
> unregister_binfmt does not set fmt->next to NULL, and seeing
> (fmt->next != NULL), register_binfmt fails with -EBUSY.
> 
> One can find his way around by explicitly setting fmt->next to NULL
> after unregistering, but that is kind of unclean (one should better be
> using only the interfaces, and not the interal members, isn't it?)
> 
> Attached one-liner can fix it (for 2.6.20).

Yes, that'll fix it.

But I wonder why register_binfmt() even checks that the to-be-registered
linux_binfmt has a non-null fmt->next?  Presumably that's there to catch
erroneous re-registration of an already-registered format.

All very odd.  It looks like that code should be converted to list_heads
anyway...