linux-kernel - Re: [PATCH -mm] tracing: Fix section mismatch in trace_hw

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Date:	Mon, 23 Feb 2009 11:21:04 +0100
From:	Markus Metzger <markus.t.metzger@...glemail.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Rakib Mullick <rakib.mullick@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, markus.t.metzger@...il.com
Subject: Re: [PATCH -mm] tracing: Fix section mismatch in trace_hw_branches.c

On Sun, Feb 22, 2009 at 5:22 PM, Frederic Weisbecker <fweisbec@...il.com> wrote:
> On Sun, Feb 22, 2009 at 07:33:08PM +0600, Rakib Mullick wrote:
>> On 2/21/09, Frederic Weisbecker <fweisbec@...il.com> wrote:

>> >  So, unless I missed something, this patch seems to me very dangerous.
>> >  The init and reset callbacks of a tracer can be called at any time, not only
>> >  on initcalls time (__init functions are freed from memory after the middle stage
>> >  of the boot).
>> >  With this patch, on UP we will dereference freed memory while activating this tracer.
>> If the init and reset callbacks of a tracer can be called regardless
>> of cpu hotpluging then it is. If the tracer's init or reset doesn't
>> rely on cpuhotplug then it shouldn't use it.
>> There's a another way to fix the warning is by remove __cpuinitdata
>> from bts_hotcpu_notifier.
[...]
> But removing __cpuinitdata will mean a kind of waste of memory (though it's only
> a little struct).

Plus the hotplug handler function. It's still not much.

I'll send out a patch following Frederic's suggestion to register the
hotplug notifier once in init.

thanks and regards,
markus.
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