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Date: Thu, 23 Jan 2003 01:41:45 -0800
From: Andrew Morton <akpm@digeo.com>
To: "dada1" <dada1@cosmosbay.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Strong kernel lock with linux-2.5.59 : futex in Huge Pages
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"dada1" <dada1@cosmosbay.com> wrote:
>
> Hello
> 
> I found a way to lock a linux-2.5.59 in all cases, in using futexes landing
> in a HugeTLB page.
> 
> You need to be root to be able to obtain HugePages (or CAP_IPC_LOCK
> capability)
> 
> I suspect that the kernel/futex.c:__pin_page(unsigned long addr) or
> mm/memory.c:follow_page() are not HugeTLB page aware.
> 
> How you can reproduce it. (dont do it of course, unless you really want to
> debug the thing)

Yup, futexes and direct-io against hugepages are bust.  I was going to fix
that up this week, but got distracted.