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Date: Wed, 9 Oct 2013 19:38:53 -0700
Message-ID: <CA+55aFxTeTOpvE7+rKD=0i0Qdn408bFCck5Eo_we=CX58UJP9Q@mail.gmail.com>
Subject: Re: [xen] double fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Dave Airlie <airlied@linux.ie>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>,
        Fengguang Wu <fengguang.wu@intel.com>, xen-devel@lists.xenproject.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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On Wed, Oct 9, 2013 at 7:23 PM, Dave Airlie <airlied@linux.ie> wrote:
>
> Well the commit that added it had a reason that seems to cover some other
> device model abuses, so maybe someone who actually understands the device
> model (all 2 people) can review usage

Actually, I think it's the same bug.

You *cannot* just reuse the storage. Doing a "memset()" doesn't
improve anything. The basic issue is that if you reuse it, you're
buggy. End of story.

Why? It's refcounted, and it's out of your hands. Reusing it is wrong
- because it might still be used. The fact that you "released" it is
immaterial. Others can have refcounts (and through /sys etc,
historically really do have them).

            Linus
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