linux-kernel - Re: debugctl msr

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Date:	Wed, 19 Nov 2008 21:53:06 +0100
From:	"stephane eranian" <eranian@...glemail.com>
To:	"Markus Metzger" <markus.t.metzger@...glemail.com>
Cc:	"Metzger, Markus T" <markus.t.metzger@...el.com>,
	"Ingo Molnar" <mingo@...e.hu>, "Andi Kleen" <andi@...stfloor.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: debugctl msr

Markus,


On Wed, Nov 19, 2008 at 8:20 PM, stephane eranian
<eranian@...glemail.com> wrote:
>
>> For a single ds_release() call matching a corresponding successful
>> ds_request() call, the buffer is freed if and only if it had been
>> allocated by ds.c.
>>
>> Kfree() itself handles NULL pointers and scripts/checkpatch.pl warns on
>> a check for NULL around a kfree() call.
>>
> Yes, I have narrowed this down to the following lines:
>        current->mm->total_vm  -= context->pages[qual];
>        current->mm->locked_vm -= context->pages[qual];

To follow-up on this, the other issue with this code is that you
should not decrease
those two mm fields  if the buffer was not allocated by ds.c. So I
think, the modification
I sent you in my patch is actually valid (just for another reason).
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