From: Christoph Lameter <clameter@sgi.com>
To: Andrea Arcangeli <andrea@qumranet.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
kvm-devel@lists.sourceforge.net, steiner@sgi.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Robin Holt <holt@sgi.com>,
general@lists.openfabrics.org,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: [ofa-general] Re: [patch 02/10] emm: notifier logic
Date: Sun, 6 Apr 2008 22:48:56 -0700 (PDT) [thread overview]
Message-ID: <Pine.LNX.4.64.0804062246030.18148@schroedinger.engr.sgi.com> (raw)
In-Reply-To: <20080405005759.GH14784@duo.random>
On Sat, 5 Apr 2008, Andrea Arcangeli wrote:
> > + rcu_assign_pointer(mm->emm_notifier, e);
> > + mm_unlock(mm);
>
> My mm_lock solution makes all rcu serialization an unnecessary
> overhead so you should remove it like I already did in #v11. If it
> wasn't the case, then mm_lock wouldn't be a definitive fix for the
> race.
There still could be junk in the cache of one cpu. If you just read the
new pointer but use the earlier content pointed to then you have a
problem.
So a memory fence / barrier is needed to guarantee that the contents
pointed to are fetched after the pointer.
next prev parent reply other threads:[~2008-04-07 5:48 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-04 22:30 [ofa-general] [patch 00/10] [RFC] EMM Notifier V3 Christoph Lameter
2008-04-04 22:30 ` [ofa-general] [patch 01/10] emm: mm_lock: Lock a process against reclaim Christoph Lameter
2008-04-04 23:12 ` [ofa-general] " Jeremy Fitzhardinge
2008-04-05 0:41 ` Andrea Arcangeli
2008-04-07 13:55 ` Peter Zijlstra
2008-04-07 19:02 ` Jeremy Fitzhardinge
2008-04-07 19:35 ` Andrea Arcangeli
2008-04-04 22:30 ` [patch 02/10] emm: notifier logic Christoph Lameter
2008-04-05 0:57 ` [ofa-general] " Andrea Arcangeli
2008-04-07 5:48 ` Christoph Lameter [this message]
2008-04-07 6:06 ` Andrea Arcangeli
2008-04-07 6:20 ` Christoph Lameter
2008-04-07 7:13 ` [ofa-general] " Andrea Arcangeli
2008-04-08 20:23 ` Christoph Lameter
2008-04-09 14:29 ` Andrea Arcangeli
2008-04-04 22:30 ` [patch 03/10] emm: Move tlb flushing into free_pgtables Christoph Lameter
2008-04-04 22:30 ` [ofa-general] [patch 04/10] emm: Convert i_mmap_lock to i_mmap_sem Christoph Lameter
2008-04-04 22:30 ` [patch 05/10] emm: Remove tlb pointer from the parameters of unmap vmas Christoph Lameter
2008-04-04 22:30 ` [ofa-general] [patch 06/10] emm: Convert anon_vma lock to rw_sem and refcount Christoph Lameter
2008-04-04 22:30 ` [patch 07/10] xpmem: This patch exports zap_page_range as it is needed by XPMEM Christoph Lameter
2008-04-04 22:30 ` [patch 08/10] xpmem: Locking rules for taking multiple mmap_sem locks Christoph Lameter
2008-04-04 22:30 ` [patch 09/10] xpmem: The device driver Christoph Lameter
2008-04-04 22:30 ` [ofa-general] [patch 10/10] xpmem: Simple example Christoph Lameter
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