From: Christoph Lameter <clameter@sgi.com>
To: Andrea Arcangeli <andrea@qumranet.com>
Cc: Nick Piggin <npiggin@suse.de>,
Steve Wise <swise@opengridcomputing.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
linux-mm@kvack.org, Kanoj Sarcar <kanojsarcar@yahoo.com>,
Roland Dreier <rdreier@cisco.com>, Jack Steiner <steiner@sgi.com>,
linux-kernel@vger.kernel.org, Avi Kivity <avi@qumranet.com>,
kvm-devel@lists.sourceforge.net, Robin Holt <holt@sgi.com>,
general@lists.openfabrics.org, akpm@linux-foundation.org
Subject: Re: [PATCH 1 of 8] Core of mmu notifiers
Date: Wed, 2 Apr 2008 18:03:50 -0700 (PDT) [thread overview]
Message-ID: <Pine.LNX.4.64.0804021758010.542@schroedinger.engr.sgi.com> (raw)
In-Reply-To: <20080403004246.GA16633@duo.random>
Thinking about this adventurous locking some more: I think you are
misunderstanding what a seqlock is. It is *not* a spinlock.
The critical read section with the reading of a version before and after
allows you access to a certain version of memory how it is or was some
time ago (caching effect). It does not mean that the current state of
memory is fixed and neither does it allow syncing when an item is added
to the list.
So it could be that you are traversing a list that is missing one item
because it is not visible to this processor yet.
You may just see a state from the past. I would think that you will need a
real lock in order to get the desired effect.
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next prev parent reply other threads:[~2008-04-03 1:03 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-02 21:30 [ofa-general] [PATCH 0 of 8] mmu notifiers #v10 Andrea Arcangeli
2008-04-02 21:30 ` [ofa-general] [PATCH 1 of 8] Core of mmu notifiers Andrea Arcangeli
2008-04-02 22:34 ` Christoph Lameter
2008-04-03 0:42 ` Andrea Arcangeli
2008-04-03 1:03 ` Christoph Lameter [this message]
2008-04-02 21:30 ` [PATCH 2 of 8] Moves all mmu notifier methods outside the PT lock (first and not last Andrea Arcangeli
2008-04-02 22:03 ` [ofa-general] " Christoph Lameter
2008-04-02 21:30 ` [PATCH 3 of 8] Move the tlb flushing into free_pgtables. The conversion of the locks Andrea Arcangeli
2008-04-02 21:30 ` [PATCH 4 of 8] The conversion to a rwsem allows callbacks during rmap traversal Andrea Arcangeli
2008-04-02 21:30 ` [ofa-general] [PATCH 5 of 8] We no longer abort unmapping in unmap vmas because we can reschedule while Andrea Arcangeli
2008-04-02 21:30 ` [PATCH 6 of 8] Convert the anon_vma spinlock to a rw semaphore. This allows concurrent Andrea Arcangeli
2008-04-02 21:30 ` [PATCH 7 of 8] XPMEM would have used sys_madvise() except that madvise_dontneed() Andrea Arcangeli
2008-04-02 21:30 ` [ofa-general] [PATCH 8 of 8] This patch adds a lock ordering rule to avoid a potential deadlock when Andrea Arcangeli
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