Date: Wed, 25 May 2005 22:52:04 -0700
From: Andrew Morton <akpm@osdl.org>
To: Shaohua Li <shaohua.li@intel.com>
Cc: pavel@ucw.cz, linux-kernel@vger.kernel.org, davidm@napali.hpl.hp.com
Subject: Re: Hotplug CPU printk issue
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Shaohua Li <shaohua.li@intel.com> wrote:
>
> > Please confirm that we in fact do not want to allow downed CPUs to
>  > print things, then send a patch.
>  Yep. In the cpu hotplug case, per-cpu data possibly isn't initialized
>  even the system state is 'running'. As the comments say in the original
>  code, some console drivers assume per-cpu resources have been allocated.
>  radeon fb is one such driver, which uses kmalloc. After a CPU is down,
>  the per-cpu data of slab is freed, so the system crashed when printing
>  some info.

hm, that certainly sounds sane, but I do recall there were
reasonable-sounding reasons why the ia64 guys wanted printk-on-a-down-CPU
to work.  Hopefully David can remember what the problem was so we can find
a more thorough fix.

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