From: Roland Dreier <rdreier@cisco.com>
To: Andrea Arcangeli <andrea@qumranet.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
Dave Jones <davej@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
David Miller <davem@davemloft.net>,
jeremy@goop.org, hugh@veritas.com, mingo@elte.hu,
akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
arjan <arjan@infradead.org>
Subject: Re: [PATCH] workaround minor lockdep bug triggered by mm_take_all_locks
Date: Mon, 04 Aug 2008 19:00:03 -0700 [thread overview]
Message-ID: <adar694rzks.fsf@cisco.com> (raw)
In-Reply-To: <20080804210954.GC12464@duo.random> (Andrea Arcangeli's message of "Mon, 4 Aug 2008 23:09:54 +0200")
> The point is that this is a runtime evaluation of lock orders, if
> runtime isn't the lucky one that reproduces the deadlock, it'll find
> nothing at all.
I think the point you miss is that lockdep can report a potential
deadlock, even if the deadlock does not actually occur. For example
suppose there is an AB-BA deadlock somewhere. For this to actually
trigger, we have to have one CPU running the AB code path at exactly the
moment another CPU runs the BA code path, with the right timing so one
CPU holds A and tries to grab B while the other CPU already holds B.
With lockdep, we just have to have the AB code path run once at any
point, and then the BA code path run at any later time (even days after
the AB code path has released all the locks). And then we get a
warning dump that explains the exact potential deadlock.
- R.
next prev parent reply other threads:[~2008-08-05 2:05 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-04 13:03 [RFC][PATCH 0/7] lockdep Peter Zijlstra
2008-08-04 13:03 ` [RFC][PATCH 1/7] lockdep: Fix combinatorial explosion in lock subgraph traversal Peter Zijlstra
2008-08-05 8:34 ` David Miller
2008-08-05 8:46 ` Peter Zijlstra
2008-08-13 3:48 ` Tim Pepper
2008-08-13 10:56 ` Ingo Molnar
2008-08-04 13:03 ` [RFC][PATCH 2/7] lockdep: lock_set_subclass - reset a held locks subclass Peter Zijlstra
2008-08-05 8:35 ` David Miller
2008-08-04 13:03 ` [RFC][PATCH 3/7] lockdep: re-annotate scheduler runqueues Peter Zijlstra
2008-08-05 8:35 ` David Miller
2008-08-04 13:03 ` [RFC][PATCH 4/7] lockdep: shrink held_lock structure Peter Zijlstra
2008-08-05 16:08 ` Peter Zijlstra
2008-08-06 7:17 ` Peter Zijlstra
2008-08-04 13:03 ` [RFC][PATCH 5/7] lockdep: map_acquire Peter Zijlstra
2008-08-04 13:03 ` [RFC][PATCH 6/7] lockdep: lock protection locks Peter Zijlstra
2008-08-04 13:03 ` [RFC][PATCH 7/7] lockdep: spin_lock_nest_lock() Peter Zijlstra
2008-08-04 14:07 ` Roland Dreier
2008-08-04 14:19 ` Peter Zijlstra
2008-08-04 14:26 ` Roland Dreier
2008-08-04 14:32 ` Peter Zijlstra
2008-08-04 14:53 ` Dave Jones
2008-08-04 14:56 ` Peter Zijlstra
2008-08-04 16:26 ` Andrea Arcangeli
2008-08-04 16:38 ` Peter Zijlstra
2008-08-04 17:27 ` Andrea Arcangeli
2008-08-04 17:46 ` Andrea Arcangeli
2008-08-04 17:57 ` [PATCH] workaround minor lockdep bug triggered by mm_take_all_locks Andrea Arcangeli
2008-08-04 18:48 ` Peter Zijlstra
2008-08-04 18:56 ` Roland Dreier
2008-08-04 19:05 ` Peter Zijlstra
2008-08-04 20:15 ` Andrea Arcangeli
2008-08-04 20:37 ` Peter Zijlstra
2008-08-04 21:09 ` Andrea Arcangeli
2008-08-04 21:14 ` Pekka Enberg
2008-08-04 21:30 ` Andrea Arcangeli
2008-08-04 21:41 ` Andrew Morton
2008-08-04 22:12 ` Andrea Arcangeli
2008-08-04 21:42 ` Arjan van de Ven
2008-08-04 22:30 ` Andrea Arcangeli
2008-08-04 23:38 ` Arjan van de Ven
2008-08-05 0:47 ` Andrea Arcangeli
2008-08-04 21:27 ` Arjan van de Ven
2008-08-04 21:54 ` Andrea Arcangeli
2008-08-04 21:57 ` David Miller
2008-08-05 2:00 ` Roland Dreier [this message]
2008-08-05 2:18 ` Andrea Arcangeli
2008-08-05 12:02 ` Roland Dreier
2008-08-05 12:20 ` Andrea Arcangeli
2008-08-04 18:48 ` [RFC][PATCH 7/7] lockdep: spin_lock_nest_lock() Peter Zijlstra
2008-08-04 21:32 ` David Miller
2008-08-04 18:06 ` Jeremy Fitzhardinge
2008-08-04 18:54 ` Peter Zijlstra
2008-08-04 19:26 ` Jeremy Fitzhardinge
2008-08-04 19:31 ` Linus Torvalds
2008-08-04 19:39 ` Peter Zijlstra
2008-08-04 20:16 ` Jeremy Fitzhardinge
2008-10-08 15:27 ` Steven Rostedt
2008-10-08 15:43 ` Linus Torvalds
2008-10-08 16:03 ` Steven Rostedt
2008-10-08 16:19 ` Linus Torvalds
2008-10-08 16:53 ` Steven Rostedt
2008-10-08 15:52 ` Nick Piggin
2008-10-08 17:18 ` Steven Rostedt
2008-08-07 11:25 ` Peter Zijlstra
2008-08-07 11:25 ` [RFC][PATCH 8/7] lockdep: annotate mm_take_all_locks() Peter Zijlstra
2008-08-07 11:25 ` [RFC][PATCH 9/7] mm: fix mm_take_all_locks() locking order Peter Zijlstra
2008-08-07 12:14 ` Hugh Dickins
2008-08-07 12:41 ` Peter Zijlstra
2008-08-07 13:27 ` Hugh Dickins
2008-08-07 21:46 ` Andrea Arcangeli
2008-08-08 1:34 ` Andrea Arcangeli
2008-08-08 7:16 ` Peter Zijlstra
2008-08-11 10:08 ` [RFC][PATCH 0/7] lockdep Ingo Molnar
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=adar694rzks.fsf@cisco.com \
--to=rdreier@cisco.com \
--cc=a.p.zijlstra@chello.nl \
--cc=akpm@linux-foundation.org \
--cc=andrea@qumranet.com \
--cc=arjan@infradead.org \
--cc=davej@redhat.com \
--cc=davem@davemloft.net \
--cc=hugh@veritas.com \
--cc=jeremy@goop.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox