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From: Andrea Arcangeli <andrea@qumranet.com>
To: Christoph Lameter <clameter@sgi.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>,
	akpm@linux-foundation.org, Robin Holt <holt@sgi.com>,
	Avi Kivity <avi@qumranet.com>, Izik Eidus <izike@qumranet.com>,
	kvm-devel@lists.sourceforge.net,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	general@lists.openfabrics.org,
	Steve Wise <swise@opengridcomputing.com>,
	Roland Dreier <rdreier@cisco.com>,
	Kanoj Sarcar <kanojsarcar@yahoo.com>,
	steiner@sgi.com, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, daniel.blueman@quadrics.com
Subject: Re: [patch 2/6] mmu_notifier: Callbacks to invalidate address ranges
Date: Thu, 28 Feb 2008 01:11:04 +0100	[thread overview]
Message-ID: <20080228001104.GB8091@v2.random> (raw)
In-Reply-To: <Pine.LNX.4.64.0802271424390.13186@schroedinger.engr.sgi.com>

On Wed, Feb 27, 2008 at 02:35:59PM -0800, Christoph Lameter wrote:
> Could you be specific? This refers to page migration? Hmmm... Guess we 

If the reader schedule, the synchronize_rcu will return in the other
cpu and the objects in the list will be freed and overwritten, and
when the task is scheduled back in, it'll follow dangling pointers...
You can't use RCU if you want any of your invalidate methods to
schedule. Otherwise it's like having zero locking.

> 2. Not handle file backed mappings (XPmem could work mostly in such a 
> config)

IMHO that fits under your definition of "hacking something in now and
then having to modify it later".

> 3. Keep the refcount elevated until pages are freed in another execution 
> context.

Page refcount is not enough (the mmu_notifier_release will run in
another cpu the moment after i_mmap_lock is unlocked) but mm_users may
prevent us to change the i_mmap_lock to a mutex, but it'll slowdown
truncate as it'll have to drop the lock and restart the radix tree
walk every time so a change like this better fits as a separate
CONFIG_XPMEM IMHO.

  parent reply	other threads:[~2008-02-28  0:11 UTC|newest]

Thread overview: 129+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-15  6:48 [patch 0/6] MMU Notifiers V7 Christoph Lameter
2008-02-15  6:49 ` [patch 1/6] mmu_notifier: Core code Christoph Lameter
2008-02-16  3:37   ` Andrew Morton
2008-02-16  8:45     ` Avi Kivity
2008-02-16  8:56       ` Andrew Morton
2008-02-16  9:21         ` Avi Kivity
2008-02-16 10:41     ` Brice Goglin
2008-02-16 10:58       ` Andrew Morton
2008-02-16 19:31         ` Christoph Lameter
2008-02-16 19:21     ` Christoph Lameter
2008-02-17  3:01       ` Andrea Arcangeli
2008-02-17 12:24         ` Robin Holt
2008-02-17  5:04     ` Doug Maxey
2008-02-18 22:33   ` Roland Dreier
2008-02-15  6:49 ` [patch 2/6] mmu_notifier: Callbacks to invalidate address ranges Christoph Lameter
2008-02-16  3:37   ` Andrew Morton
2008-02-16 19:26     ` Christoph Lameter
2008-02-19  8:54   ` Nick Piggin
2008-02-19 13:34     ` Andrea Arcangeli
2008-02-27 22:23       ` Christoph Lameter
2008-02-27 23:57         ` Andrea Arcangeli
2008-02-19 23:08   ` Nick Piggin
2008-02-20  1:00     ` Andrea Arcangeli
2008-02-20  3:00       ` Robin Holt
2008-02-20  3:11         ` Nick Piggin
2008-02-20  3:19           ` Robin Holt
2008-02-27 22:39       ` Christoph Lameter
2008-02-28  0:38         ` Andrea Arcangeli
2008-02-27 22:35     ` Christoph Lameter
2008-02-27 22:42       ` Jack Steiner
2008-02-28  0:10       ` Christoph Lameter
2008-02-28  0:11       ` Andrea Arcangeli [this message]
2008-02-28  0:14         ` Christoph Lameter
2008-02-28  0:52           ` Andrea Arcangeli
2008-02-28  1:03             ` Christoph Lameter
2008-02-28  1:10               ` Andrea Arcangeli
2008-02-28 18:43                 ` Christoph Lameter
2008-02-29  0:55                   ` Andrea Arcangeli
2008-02-29  0:59                     ` Christoph Lameter
2008-02-29 13:13                       ` Andrea Arcangeli
2008-02-29 19:55                         ` Christoph Lameter
2008-02-29 20:17                           ` Andrea Arcangeli
2008-02-29 21:03                             ` Christoph Lameter
2008-02-29 21:23                               ` Andrea Arcangeli
2008-02-29 21:29                                 ` Christoph Lameter
2008-02-29 21:34                                 ` Christoph Lameter
2008-02-29 21:48                                   ` Andrea Arcangeli
2008-02-29 22:12                                     ` Christoph Lameter
2008-02-29 22:41                                       ` Andrea Arcangeli
2008-02-28 10:53             ` Robin Holt
2008-03-03  5:11       ` Nick Piggin
2008-03-03 19:28         ` Christoph Lameter
2008-03-03 19:50           ` Nick Piggin
2008-03-04 18:58             ` Christoph Lameter
2008-03-05  0:52               ` Nick Piggin
2008-02-15  6:49 ` [patch 3/6] mmu_notifier: invalidate_page callbacks Christoph Lameter
2008-02-16  3:37   ` Andrew Morton
2008-02-16 11:07     ` Andrea Arcangeli
2008-02-16 19:22     ` Christoph Lameter
2008-02-16 19:54       ` Avi Kivity
2008-02-19  8:46       ` Nick Piggin
2008-02-19 13:30         ` Andrea Arcangeli
2008-02-18  1:51     ` Nick Piggin
2008-02-15  6:49 ` [patch 4/6] mmu_notifier: Skeleton driver for a simple mmu_notifier Christoph Lameter
2008-02-15  6:49 ` [patch 5/6] mmu_notifier: Support for drivers with revers maps (f.e. for XPmem) Christoph Lameter
2008-02-16  3:37   ` Andrew Morton
2008-02-16 19:28     ` Christoph Lameter
2008-02-19 23:55   ` Nick Piggin
2008-02-20  3:12     ` Robin Holt
2008-02-20  3:51       ` Nick Piggin
2008-02-20  9:00         ` Robin Holt
2008-02-20  9:05           ` Robin Holt
2008-02-21  4:20           ` Nick Piggin
2008-02-21 10:58             ` Robin Holt
2008-02-26  6:11               ` Nick Piggin
2008-02-26  7:21                 ` [ofa-general] " Gleb Natapov
2008-02-26  8:52                   ` Nick Piggin
2008-02-26  9:38                     ` Gleb Natapov
2008-02-26  9:52                       ` KOSAKI Motohiro
2008-02-26 12:28                     ` Robin Holt
2008-02-26 12:29                 ` Robin Holt
2008-02-27 22:43     ` Christoph Lameter
2008-02-28  0:42       ` Andrea Arcangeli
2008-02-28  1:01         ` Christoph Lameter
2008-02-15  6:49 ` [patch 6/6] mmu_rmap_notifier: Skeleton for complex driver that uses its own rmaps Christoph Lameter
2008-02-16 10:48 ` [PATCH] KVM swapping with MMU Notifiers V7 Andrea Arcangeli
2008-02-16 11:08   ` Andrew Morton
2008-02-18 12:17     ` Andrea Arcangeli
2008-02-16 11:51   ` Robin Holt
2008-02-18 12:35     ` Andrea Arcangeli
  -- strict thread matches above, loose matches on Subject: below --
2008-02-08 22:06 [patch 0/6] MMU Notifiers V6 Christoph Lameter
2008-02-08 22:06 ` [patch 2/6] mmu_notifier: Callbacks to invalidate address ranges Christoph Lameter
2008-01-30  2:29 [patch 0/6] [RFC] MMU Notifiers V3 Christoph Lameter
2008-01-30  2:29 ` [patch 2/6] mmu_notifier: Callbacks to invalidate address ranges Christoph Lameter
2008-01-28 20:28 [patch 0/6] [RFC] MMU Notifiers V2 Christoph Lameter
2008-01-28 20:28 ` [patch 2/6] mmu_notifier: Callbacks to invalidate address ranges Christoph Lameter
2008-01-29 16:20   ` Andrea Arcangeli
2008-01-29 18:28     ` Andrea Arcangeli
2008-01-29 20:30       ` Christoph Lameter
2008-01-29 21:36         ` Andrea Arcangeli
2008-01-29 21:53           ` Christoph Lameter
2008-01-29 22:35             ` Andrea Arcangeli
2008-01-29 22:55               ` Christoph Lameter
2008-01-29 23:43                 ` Andrea Arcangeli
2008-01-30  0:34                   ` Christoph Lameter
2008-01-29 19:55     ` Christoph Lameter
2008-01-29 21:17       ` Andrea Arcangeli
2008-01-29 21:35         ` Christoph Lameter
2008-01-29 22:02           ` Andrea Arcangeli
2008-01-29 22:39             ` Christoph Lameter
2008-01-30  0:00               ` Andrea Arcangeli
2008-01-30  0:05                 ` Andrea Arcangeli
2008-01-30  0:22                   ` Christoph Lameter
2008-01-30  0:59                     ` Andrea Arcangeli
2008-01-30  8:26                       ` Peter Zijlstra
2008-01-30  0:20                 ` Christoph Lameter
2008-01-30  0:28                   ` Jack Steiner
2008-01-30  0:35                     ` Christoph Lameter
2008-01-30 13:37                     ` Andrea Arcangeli
2008-01-30 14:43                       ` Jack Steiner
2008-01-30 19:41                         ` Christoph Lameter
2008-01-30 20:29                           ` Jack Steiner
2008-01-30 20:55                             ` Christoph Lameter
2008-01-30 16:11                 ` Robin Holt
2008-01-30 17:04                   ` Andrea Arcangeli
2008-01-30 17:30                     ` Robin Holt
2008-01-30 18:25                       ` Andrea Arcangeli
2008-01-30 19:50                         ` Christoph Lameter
2008-01-30 22:18                           ` Robin Holt
2008-01-30 23:52                           ` Andrea Arcangeli
2008-01-31  0:01                             ` Christoph Lameter
2008-01-30 19:35                   ` Christoph Lameter

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