From: Linus Torvalds <torvalds@linux-foundation.org>
To: Borislav Petkov <bp@alien8.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Rik van Riel <riel@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Minchan Kim <minchan.kim@gmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Lee Schermerhorn <Lee.Schermerhorn@hp.com>,
Nick Piggin <npiggin@suse.de>,
Andrea Arcangeli <aarcange@redhat.com>,
Hugh Dickins <hugh.dickins@tiscali.co.uk>,
sgunderson@bigfoot.com
Subject: Re: [PATCH -v2] rmap: make anon_vma_prepare link in all the anon_vmas of a mergeable VMA
Date: Sun, 11 Apr 2010 10:16:10 -0700 (PDT) [thread overview]
Message-ID: <alpine.LFD.2.00.1004111010280.3514@i5.linux-foundation.org> (raw)
In-Reply-To: <alpine.LFD.2.00.1004110938570.3514@i5.linux-foundation.org>
On Sun, 11 Apr 2010, Linus Torvalds wrote:
>
> But I think the bug you see might be exactly the race between
> page_mapped() and actually getting the anon_vma spinlock. I'd have
> expected that window to be too small to ever hit, though, which is why I
> find it a bit unlikely. But it would explain why you _sometimes_
> actually get a hung spinlock too - you never get the spinlock at all,
> and somebody replaced the data with something that the spinlock code
> thinks is a locked spinlock - but is no longer a spinlock at all ]
Actually, so if it's that race, then we might get rid of the oops with
this total hack.
NOTE! If this is the race, then the hack really is just a hack, because it
doesn't really solve anything. We still take the spinlock, and if bad
things has happened, _that_ can still very much fail, and you get the
watchdog lockup message instead. So this doesn't really fix anything.
But if this patch changes behavior, and you no longer see the oops, that
tells us _something_. I'm not sure how useful that "something" is, but it
at least means that there are no _mapped_ pages that have that stale
anon_vma pointer in page->mapping.
Conversely, if you still see the oops (rather than the watchdog), that
means that we actually have pages that are still marked mapped, and that
despite that mapped state have a stale page->mapping pointer. I actually
find that the more likely case, because otherwise the window is _so_ small
that I don't see how you can hit the oops so reliably.
Anyway - probably worth testing, along with the verify_vma() patch. If
nothing else, if there is no new behavior, even that tells us something.
Even if that "something" is not a huge piece of information.
Linus
---
diff --git a/mm/rmap.c b/mm/rmap.c
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -302,7 +302,11 @@ struct anon_vma *page_lock_anon_vma(struct page *page)
anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
spin_lock(&anon_vma->lock);
- return anon_vma;
+
+ if (page_mapped(page))
+ return anon_vma;
+
+ spin_unlock(&anon_vma->lock);
out:
rcu_read_unlock();
return NULL;
next prev parent reply other threads:[~2010-04-11 17:20 UTC|newest]
Thread overview: 231+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-30 17:50 Linux 2.6.34-rc3 Linus Torvalds
2010-03-30 21:16 ` [Regression, post-rc2] Commit a5ee4eb7541 breaks OpenGL on RS780 (was: Re: Linux 2.6.34-rc3) Rafael J. Wysocki
2010-03-31 20:34 ` [stable] " Greg KH
2010-04-01 1:13 ` Rafael J. Wysocki
2010-04-01 2:19 ` Alex Deucher
2010-04-01 6:36 ` Clemens Ladisch
2010-04-01 15:01 ` Alex Deucher
2010-04-01 20:28 ` Rafael J. Wysocki
2010-04-01 20:39 ` Alex Deucher
2010-04-01 20:48 ` Rafael J. Wysocki
2010-04-01 21:00 ` Alex Deucher
2010-04-01 21:01 ` Alex Deucher
2010-04-01 21:08 ` Rafael J. Wysocki
2010-04-01 21:13 ` Alex Deucher
2010-04-01 21:46 ` Rafael J. Wysocki
2010-04-01 22:07 ` Alex Deucher
2010-04-01 23:20 ` Rafael J. Wysocki
2010-04-02 0:23 ` Linus Torvalds
2010-04-02 16:46 ` Rafael J. Wysocki
2010-04-03 18:08 ` Clemens Ladisch
2010-04-03 19:33 ` Rafael J. Wysocki
2010-04-01 16:29 ` Linus Torvalds
2010-04-01 17:07 ` Alex Deucher
2010-04-01 17:24 ` Linus Torvalds
2010-04-01 17:50 ` [Regression, post-rc2] Commit a5ee4eb7541 breaks OpenGL on RS780 Clemens Ladisch
2010-04-01 17:53 ` [Regression, post-rc2] Commit a5ee4eb7541 breaks OpenGL on RS780 (was: Re: Linux 2.6.34-rc3) Alex Deucher
2010-04-01 20:17 ` Linus Torvalds
2010-04-01 20:23 ` Alex Deucher
2010-04-01 19:46 ` Rafael J. Wysocki
2010-04-01 22:48 ` Jesse Barnes
2010-04-01 23:23 ` Rafael J. Wysocki
2010-04-02 17:59 ` Ugly rmap NULL ptr deref oopsie on hibernate (was " Borislav Petkov
2010-04-02 18:09 ` Linus Torvalds
2010-04-02 15:24 ` Andrew Morton
2010-04-02 18:37 ` Linus Torvalds
2010-04-02 22:01 ` Rik van Riel
2010-04-03 0:19 ` Linus Torvalds
2010-04-04 16:12 ` Minchan Kim
2010-04-04 17:24 ` Rik van Riel
2010-04-04 23:09 ` [PATCH] rmap: fix anon_vma_fork() memory leak Rik van Riel
2010-04-04 23:56 ` Minchan Kim
2010-04-05 15:37 ` Linus Torvalds
2010-04-05 15:48 ` Minchan Kim
2010-04-05 16:04 ` Rik van Riel
2010-04-05 16:13 ` [PATCH -v2] " Rik van Riel
2010-04-06 8:53 ` Ugly rmap NULL ptr deref oopsie on hibernate (was Linux 2.6.34-rc3) KOSAKI Motohiro
2010-04-06 10:09 ` KOSAKI Motohiro
2010-04-06 14:34 ` Rik van Riel
2010-04-06 14:38 ` Rik van Riel
2010-04-06 15:34 ` Minchan Kim
2010-04-06 15:40 ` Rik van Riel
2010-04-06 15:58 ` Minchan Kim
2010-04-06 15:55 ` Linus Torvalds
2010-04-06 16:23 ` Minchan Kim
2010-04-06 16:28 ` Linus Torvalds
2010-04-06 16:45 ` Minchan Kim
2010-04-06 16:53 ` Linus Torvalds
2010-04-06 17:04 ` Rik van Riel
2010-04-06 18:28 ` Linus Torvalds
2010-04-06 19:03 ` Andrew Morton
2010-04-06 19:10 ` Steinar H. Gunderson
2010-04-06 19:10 ` Linus Torvalds
2010-04-06 19:35 ` Linus Torvalds
2010-04-06 19:42 ` Borislav Petkov
2010-04-06 20:02 ` Linus Torvalds
2010-04-06 20:46 ` Steinar H. Gunderson
2010-04-06 20:56 ` Linus Torvalds
2010-04-06 21:05 ` Steinar H. Gunderson
2010-04-06 20:51 ` Borislav Petkov
2010-04-06 21:27 ` Linus Torvalds
2010-04-06 22:59 ` Borislav Petkov
2010-04-06 23:27 ` Linus Torvalds
2010-04-06 23:54 ` [PATCH] rmap: make anon_vma_prepare link in all the anon_vmas of a mergeable VMA Rik van Riel
2010-04-07 7:00 ` KOSAKI Motohiro
2010-04-07 14:48 ` Rik van Riel
2010-04-07 14:54 ` [PATCH -v2] " Rik van Riel
2010-04-07 15:30 ` Linus Torvalds
2010-04-07 15:52 ` Rik van Riel
2010-04-07 16:56 ` Linus Torvalds
2010-04-07 21:19 ` Linus Torvalds
2010-04-07 21:52 ` Rik van Riel
2010-04-07 22:09 ` Linus Torvalds
2010-04-07 22:15 ` Linus Torvalds
2010-04-08 0:38 ` Rik van Riel
2010-04-07 23:37 ` Linus Torvalds
2010-04-08 2:03 ` KOSAKI Motohiro
2010-04-08 2:33 ` Linus Torvalds
2010-04-08 5:47 ` Borislav Petkov
2010-04-08 14:11 ` Linus Torvalds
2010-04-08 18:25 ` Rik van Riel
2010-04-08 18:32 ` Linus Torvalds
2010-04-08 20:31 ` Borislav Petkov
2010-04-08 21:00 ` Borislav Petkov
2010-04-08 23:16 ` Linus Torvalds
2010-04-08 23:47 ` Borislav Petkov
2010-04-09 0:50 ` Linus Torvalds
2010-04-09 1:30 ` Borislav Petkov
2010-04-09 9:21 ` Borislav Petkov
2010-04-09 16:35 ` Linus Torvalds
2010-04-09 17:40 ` Borislav Petkov
2010-04-09 17:50 ` Linus Torvalds
2010-04-09 19:14 ` Borislav Petkov
2010-04-09 19:32 ` Linus Torvalds
2010-04-09 20:03 ` Rik van Riel
2010-04-09 20:43 ` Johannes Weiner
2010-04-09 20:57 ` Rik van Riel
2010-04-09 21:33 ` Borislav Petkov
2010-04-09 23:22 ` Linus Torvalds
2010-04-09 23:45 ` Rik van Riel
2010-04-10 0:03 ` Linus Torvalds
2010-04-10 0:11 ` Rik van Riel
2010-04-09 23:54 ` Johannes Weiner
2010-04-09 23:56 ` Linus Torvalds
2010-04-10 0:19 ` Rik van Riel
2010-04-10 0:31 ` Johannes Weiner
2010-04-10 0:32 ` Linus Torvalds
2010-04-10 7:27 ` Borislav Petkov
2010-04-10 11:26 ` Borislav Petkov
2010-04-10 14:45 ` Rik van Riel
2010-04-10 15:24 ` Linus Torvalds
2010-04-10 16:38 ` Borislav Petkov
2010-04-10 17:05 ` Linus Torvalds
2010-04-10 18:21 ` Linus Torvalds
2010-04-10 18:26 ` Linus Torvalds
2010-04-10 18:51 ` Borislav Petkov
2010-04-10 18:58 ` Borislav Petkov
2010-04-10 20:05 ` Linus Torvalds
2010-04-10 20:12 ` Linus Torvalds
2010-04-10 20:36 ` Borislav Petkov
2010-04-10 20:40 ` Linus Torvalds
2010-04-10 21:25 ` Borislav Petkov
2010-04-10 21:30 ` Linus Torvalds
2010-04-10 21:51 ` Borislav Petkov
2010-04-11 13:08 ` Borislav Petkov
2010-04-11 13:19 ` [PATCH 1/3] mm: make page freeing path RCU-safe Borislav Petkov
2010-04-11 13:19 ` [PATCH 2/3] mm: cleanup find_mergeable_anon_vma complexity Borislav Petkov
2010-04-11 13:19 ` [PATCH 3/3] mm: fixup vma_adjust Borislav Petkov
2010-04-11 13:25 ` [PATCH 2/3] mm: cleanup find_mergeable_anon_vma complexity Borislav Petkov
2010-04-11 17:07 ` [PATCH -v2] rmap: make anon_vma_prepare link in all the anon_vmas of a mergeable VMA Linus Torvalds
2010-04-11 17:16 ` Linus Torvalds [this message]
2010-04-11 18:55 ` Borislav Petkov
2010-04-12 0:13 ` Linus Torvalds
2010-04-12 1:04 ` Linus Torvalds
2010-04-12 7:20 ` Borislav Petkov
2010-04-12 16:02 ` Linus Torvalds
2010-04-12 16:26 ` Linus Torvalds
2010-04-12 18:40 ` Rik van Riel
2010-04-12 19:00 ` Borislav Petkov
2010-04-12 19:17 ` Linus Torvalds
2010-04-12 20:22 ` [PATCH 1/4] Simplify and comment on anon_vma re-use for anon_vma_prepare() Linus Torvalds
2010-04-12 20:23 ` [PATCH 2/4] vma_adjust: fix the copying of anon_vma chains Linus Torvalds
2010-04-12 20:23 ` [PATCH 3/4] anon_vma: clone the anon_vma chain in the right order Linus Torvalds
2010-04-12 20:23 ` [PATCH 4/4] anonvma: when setting up page->mapping, we need to pick the _oldest_ anonvma Linus Torvalds
2010-04-12 21:03 ` Rik van Riel
2010-04-13 0:41 ` Johannes Weiner
2010-04-13 1:08 ` Linus Torvalds
2010-04-13 4:23 ` Minchan Kim
2010-04-13 4:26 ` Minchan Kim
2010-04-12 20:57 ` [PATCH 3/4] anon_vma: clone the anon_vma chain in the right order Rik van Riel
2010-04-13 0:18 ` Johannes Weiner
2010-04-13 4:16 ` Minchan Kim
2010-04-12 20:54 ` [PATCH 2/4] vma_adjust: fix the copying of anon_vma chains Rik van Riel
2010-04-12 23:59 ` Johannes Weiner
2010-04-13 4:15 ` Minchan Kim
2010-04-12 20:54 ` [PATCH 1/4] Simplify and comment on anon_vma re-use for anon_vma_prepare() Rik van Riel
2010-04-12 23:54 ` Johannes Weiner
2010-04-13 4:04 ` Minchan Kim
2010-04-13 9:51 ` Peter Zijlstra
2010-04-12 21:50 ` [PATCH -v2] rmap: make anon_vma_prepare link in all the anon_vmas of a mergeable VMA Borislav Petkov
2010-04-12 22:11 ` Linus Torvalds
2010-04-12 22:18 ` Linus Torvalds
2010-04-12 22:29 ` Borislav Petkov
2010-04-13 9:38 ` Borislav Petkov
2010-04-14 21:59 ` [PATCH] rmap: add exclusively owned pages to the newest anon_vma Rik van Riel
2010-04-14 23:20 ` Johannes Weiner
2010-04-15 8:34 ` Borislav Petkov
2010-04-15 16:02 ` Minchan Kim
2010-04-15 20:01 ` Linus Torvalds
2010-04-16 6:09 ` Felipe Balbi
2010-04-16 14:48 ` Linus Torvalds
2010-04-11 19:49 ` [PATCH -v2] rmap: make anon_vma_prepare link in all the anon_vmas of a mergeable VMA Rik van Riel
2010-04-12 15:44 ` Linus Torvalds
2010-04-12 15:51 ` Rik van Riel
2010-04-11 21:45 ` Rik van Riel
2010-04-12 15:51 ` Linus Torvalds
2010-04-13 10:36 ` KOSAKI Motohiro
2010-04-10 20:24 ` Rik van Riel
2010-04-10 20:34 ` Linus Torvalds
2010-04-10 20:43 ` Rik van Riel
2010-04-10 20:32 ` Rik van Riel
2010-04-10 19:36 ` Rik van Riel
2010-04-12 14:40 ` Peter Zijlstra
2010-04-12 15:17 ` Minchan Kim
2010-04-12 15:33 ` Peter Zijlstra
2010-04-12 15:19 ` Rik van Riel
2010-04-12 16:01 ` Peter Zijlstra
2010-04-12 16:06 ` Rik van Riel
2010-04-12 16:46 ` Linus Torvalds
2010-04-12 18:40 ` Peter Zijlstra
2010-04-12 19:30 ` Peter Zijlstra
2010-04-12 19:44 ` Peter Zijlstra
2010-04-13 10:53 ` KOSAKI Motohiro
2010-04-13 11:30 ` Peter Zijlstra
2010-04-13 12:00 ` KOSAKI Motohiro
2010-04-14 14:27 ` Peter Zijlstra
2010-04-10 17:07 ` Borislav Petkov
2010-04-10 16:41 ` Linus Torvalds
2010-04-10 22:49 ` Johannes Weiner
2010-04-10 23:31 ` Linus Torvalds
2010-04-09 1:45 ` KOSAKI Motohiro
2010-04-07 15:55 ` Minchan Kim
2010-04-07 7:29 ` Ugly rmap NULL ptr deref oopsie on hibernate (was Linux 2.6.34-rc3) Borislav Petkov
2010-04-07 14:05 ` Paulo Marques
2010-04-07 14:13 ` Borislav Petkov
2010-04-06 23:37 ` Linus Torvalds
2010-04-06 23:22 ` Rik van Riel
2010-04-07 0:10 ` Linus Torvalds
2010-04-07 1:18 ` Rik van Riel
2010-04-07 7:22 ` Borislav Petkov
2010-04-07 10:09 ` Pekka Enberg
2010-04-07 10:12 ` KOSAKI Motohiro
2010-04-07 8:41 ` Peter Zijlstra
2010-04-07 8:36 ` Peter Zijlstra
2010-04-07 9:16 ` Johannes Weiner
2010-04-07 9:37 ` Peter Zijlstra
2010-04-07 14:12 ` Rik van Riel
2010-04-07 15:46 ` Linus Torvalds
2010-04-06 16:32 ` Linus Torvalds
2010-04-06 16:54 ` Minchan Kim
2010-04-07 8:37 ` Peter Zijlstra
2010-04-06 17:05 ` Borislav Petkov
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