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Message-ID: <1337048075-6132-53-git-send-email-paul.gortmaker@windriver.com>
Date: Mon, 14 May 2012 22:12:28 -0400
From: Paul Gortmaker <paul.gortmaker@...driver.com>
To: <stable@...nel.org>, <linux-kernel@...r.kernel.org>
Subject: [34-longterm 052/179] lockdep: Fix lock_is_held() on recursion
From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
-------------------
This is a commit scheduled for the next v2.6.34 longterm release.
http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
If you see a problem with using this for longterm, please comment.
-------------------
commit f2513cde93f0957d5dc6c09bc24b0cccd27d8e1d upstream.
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@...-jansens.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Link: http://lkml.kernel.org/r/1307398759.2497.966.camel@laptop
Signed-off-by: Ingo Molnar <mingo@...e.hu>
Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
---
kernel/lockdep.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 2594e1c..1571452 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -3240,7 +3240,7 @@ 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);
--
1.7.9.6
--
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