* [PATCH] lockdep: Fix lock_is_held on recursion
@ 2011-06-06 22:19 Peter Zijlstra
2011-06-07 12:02 ` [tip:sched/urgent] lockdep: Fix lock_is_held() " tip-bot for Peter Zijlstra
0 siblings, 1 reply; 4+ messages in thread
From: Peter Zijlstra @ 2011-06-06 22:19 UTC (permalink / raw)
To: Ingo Molnar
Cc: Arne Jansen, Linus Torvalds, mingo, hpa, linux-kernel, efault,
npiggin, akpm, frank.rowand, tglx
Subject: lockdep: Fix lock_is_held on recursion
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Mon Jun 06 12:32:43 CEST 2011
The main lock_is_held() user is lockdep_assert_held(), avoid false
assertions in lockdep_off() sections by unconditionally reporting the
lock is taken.
[ the reason this is important is a lockdep_assert_held() in ttwu()
which triggers a warning under lockdep_off() as in printk() which
can trigger another wakeup and lock up due to spinlock recursion ]
Reported-and-tested-by: Arne Jansen <lists@die-jansens.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
Index: linux-2.6/kernel/lockdep.c
===================================================================
--- linux-2.6.orig/kernel/lockdep.c
+++ linux-2.6/kernel/lockdep.c
@@ -3426,7 +3426,7 @@ int lock_is_held(struct lockdep_map *loc
int ret = 0;
if (unlikely(current->lockdep_recursion))
- return ret;
+ return 1; /* avoid false negative lockdep_assert_held */
raw_local_irq_save(flags);
check_flags(flags);
^ permalink raw reply [flat|nested] 4+ messages in thread
* [tip:sched/urgent] lockdep: Fix lock_is_held() on recursion
2011-06-06 22:19 [PATCH] lockdep: Fix lock_is_held on recursion Peter Zijlstra
@ 2011-06-07 12:02 ` tip-bot for Peter Zijlstra
2011-06-07 12:39 ` Peter Zijlstra
0 siblings, 1 reply; 4+ messages in thread
From: tip-bot for Peter Zijlstra @ 2011-06-07 12:02 UTC (permalink / raw)
To: linux-tip-commits
Cc: linux-kernel, hpa, mingo, torvalds, a.p.zijlstra, lists, stable,
tglx, mingo
Commit-ID: f2513cde93f0957d5dc6c09bc24b0cccd27d8e1d
Gitweb: http://git.kernel.org/tip/f2513cde93f0957d5dc6c09bc24b0cccd27d8e1d
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Mon, 6 Jun 2011 12:32:43 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Tue, 7 Jun 2011 12:25:50 +0200
lockdep: Fix lock_is_held() on recursion
The main lock_is_held() user is lockdep_assert_held(), avoid false
assertions in lockdep_off() sections by unconditionally reporting the
lock is taken.
[ the reason this is important is a lockdep_assert_held() in ttwu()
which triggers a warning under lockdep_off() as in printk() which
can trigger another wakeup and lock up due to spinlock
recursion, as reported and heroically debugged by Arne Jansen ]
Reported-and-tested-by: Arne Jansen <lists@die-jansens.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: <stable@kernel.org>
Link: http://lkml.kernel.org/r/1307398759.2497.966.camel@laptop
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
kernel/lockdep.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 63437d0..298c927 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -3426,7 +3426,7 @@ int lock_is_held(struct lockdep_map *lock)
int ret = 0;
if (unlikely(current->lockdep_recursion))
- return ret;
+ return 1; /* avoid false negative lockdep_assert_held() */
raw_local_irq_save(flags);
check_flags(flags);
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [tip:sched/urgent] lockdep: Fix lock_is_held() on recursion
2011-06-07 12:02 ` [tip:sched/urgent] lockdep: Fix lock_is_held() " tip-bot for Peter Zijlstra
@ 2011-06-07 12:39 ` Peter Zijlstra
2011-06-07 18:06 ` Ingo Molnar
0 siblings, 1 reply; 4+ messages in thread
From: Peter Zijlstra @ 2011-06-07 12:39 UTC (permalink / raw)
To: lists, mingo, hpa, linux-kernel, torvalds, stable, tglx, mingo
Cc: linux-tip-commits
On Tue, 2011-06-07 at 12:02 +0000, tip-bot for Peter Zijlstra wrote:
> Commit-ID: f2513cde93f0957d5dc6c09bc24b0cccd27d8e1d
> Gitweb: http://git.kernel.org/tip/f2513cde93f0957d5dc6c09bc24b0cccd27d8e1d
> Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
> AuthorDate: Mon, 6 Jun 2011 12:32:43 +0200
> Committer: Ingo Molnar <mingo@elte.hu>
> CommitDate: Tue, 7 Jun 2011 12:25:50 +0200
>
> lockdep: Fix lock_is_held() on recursion
>
> The main lock_is_held() user is lockdep_assert_held(), avoid false
> assertions in lockdep_off() sections by unconditionally reporting the
> lock is taken.
>
> [ the reason this is important is a lockdep_assert_held() in ttwu()
> which triggers a warning under lockdep_off() as in printk() which
> can trigger another wakeup and lock up due to spinlock
> recursion, as reported and heroically debugged by Arne Jansen ]
>
> Reported-and-tested-by: Arne Jansen <lists@die-jansens.de>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: <stable@kernel.org>
Not _that_ critical for stable since the offending lockdep_assert_held()
doesn't exist in .39, still definitely won't hurt.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [tip:sched/urgent] lockdep: Fix lock_is_held() on recursion
2011-06-07 12:39 ` Peter Zijlstra
@ 2011-06-07 18:06 ` Ingo Molnar
0 siblings, 0 replies; 4+ messages in thread
From: Ingo Molnar @ 2011-06-07 18:06 UTC (permalink / raw)
To: Peter Zijlstra
Cc: lists, mingo, hpa, linux-kernel, torvalds, stable, tglx,
linux-tip-commits
* Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> On Tue, 2011-06-07 at 12:02 +0000, tip-bot for Peter Zijlstra wrote:
> > Commit-ID: f2513cde93f0957d5dc6c09bc24b0cccd27d8e1d
> > Gitweb: http://git.kernel.org/tip/f2513cde93f0957d5dc6c09bc24b0cccd27d8e1d
> > Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
> > AuthorDate: Mon, 6 Jun 2011 12:32:43 +0200
> > Committer: Ingo Molnar <mingo@elte.hu>
> > CommitDate: Tue, 7 Jun 2011 12:25:50 +0200
> >
> > lockdep: Fix lock_is_held() on recursion
> >
> > The main lock_is_held() user is lockdep_assert_held(), avoid false
> > assertions in lockdep_off() sections by unconditionally reporting the
> > lock is taken.
> >
> > [ the reason this is important is a lockdep_assert_held() in ttwu()
> > which triggers a warning under lockdep_off() as in printk() which
> > can trigger another wakeup and lock up due to spinlock
> > recursion, as reported and heroically debugged by Arne Jansen ]
> >
> > Reported-and-tested-by: Arne Jansen <lists@die-jansens.de>
> > Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> > Cc: Linus Torvalds <torvalds@linux-foundation.org>
> > Cc: <stable@kernel.org>
>
> Not _that_ critical for stable since the offending lockdep_assert_held()
> doesn't exist in .39, still definitely won't hurt.
Correct, the bug was hard enough to find, i didnt want someone else
to trigger a similar one. There's numerous lockdep_assert_held()
instances all around the tree.
Thanks,
Ingo
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2011-06-07 18:06 UTC | newest]
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2011-06-06 22:19 [PATCH] lockdep: Fix lock_is_held on recursion Peter Zijlstra
2011-06-07 12:02 ` [tip:sched/urgent] lockdep: Fix lock_is_held() " tip-bot for Peter Zijlstra
2011-06-07 12:39 ` Peter Zijlstra
2011-06-07 18:06 ` Ingo Molnar
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