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[xfs-masters] Re: Linux 2.6.17-rc2 - notifier chain problem?

To: Chandra Seetharaman <sekharan@xxxxxxxxxx>
Subject: [xfs-masters] Re: Linux 2.6.17-rc2 - notifier chain problem?
From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Date: Sat, 29 Apr 2006 11:30:55 -0400 (EDT)
Cc: Andrew Morton <akpm@xxxxxxxx>, <torvalds@xxxxxxxx>, <ashok.raj@xxxxxxxxx>, <herbert@xxxxxxxxxxxx>, <linux-kernel@xxxxxxxxxxxxxxx>, <linux-xfs@xxxxxxxxxxx>, <xfs-masters@xxxxxxxxxxx>
In-reply-to: <1146267809.7063.141.camel@linuxchandra>
Reply-to: xfs-masters@xxxxxxxxxxx
Sender: xfs-masters-bounce@xxxxxxxxxxx
On Fri, 28 Apr 2006, Chandra Seetharaman wrote:

> - if we are ok with a loss of a kbyte or two, 2.6.17 is fine as is 
>   (with my incorrect patches in).
> - if we want to save that memory, we can revert the two patches and fix
>   xfs to make the register calls only when hotplug cpu is defined. This
>   change is also minimal. It is a step in the right direction.
> 
> Only downside i can see in reverting my patch is that if there is any
> other modules that are doing the same as what xfs was doing, we might
> trip in a similar oops.

Once register_cpu_notifier is placed in an init section, everything should
be okay.  If some other module does _exactly_ what xfs did, it won't oops
-- instead the module will get an unresolved symbol error whenever someone
tries to insmod it, because the register_cpu_notifier symbol won't be
defined.  I think this is an appropriate kind of failure mode.

However, it wouldn't hurt to add some comments to the definition and 
declaration of register_cpu_notifier, explaining the circumstances in 
which it should be used.

Alan Stern


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