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Date:      Tue, 1 Mar 2005 15:14:38 -0800
From:      Kris Kennaway <kris@obsecurity.org>
To:        Bosko Milekic <bosko.milekic@gmail.com>
Cc:        bmilekic@freebsd.org
Subject:   Re: Race condition in mb_free_ext()?
Message-ID:  <20050301231438.GA25573@xor.obsecurity.org>
In-Reply-To: <bbebbd3d0503011504560a94b4@mail.gmail.com>
References:  <20050301000436.GA33346@xor.obsecurity.org> <200503011340.18162.jhb@FreeBSD.org> <bbebbd3d0503011504560a94b4@mail.gmail.com>

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On Tue, Mar 01, 2005 at 06:04:27PM -0500, Bosko Milekic wrote:

> This does not appear to explain the livelock.

alc and dwhite tracked it down to a missing volatile causing gcc to
mis-optimize the loop:

-               cnt = *(m->m_ext.ref_cnt);
+               cnt = *(volatile u_int *)(m->m_ext.ref_cnt);

I'm currently testing that.

Kris
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