linux-kernel - Re: 2.6.24-rc8-mm1 and boot lockup during locking self-test

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Date:	Fri, 18 Jan 2008 10:14:22 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Zan Lynx <zlynx@....org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: 2.6.24-rc8-mm1 and boot lockup during locking self-test


* Zan Lynx <zlynx@....org> wrote:

> Included Ingo in CC because I think he did the locking test.
> 
> The following is copied from a different boot, but looks the same to my
> eye as what I got on the console:
> 
> ------------------------
> | Locking API testsuite:
> ----------------------------------------------------------------------------
>                                  | spin |wlock |rlock |mutex | wsem | rsem |
>   --------------------------------------------------------------------------
>                      A-A deadlock:  ok  |
> 
> It just sticks there.  I assume that means a problem with wlock?

does the patch below from Nick fix it? It went upstream just after 
rc8-mm1 so rc8-mm1 might be missing it.

	Ingo

------------------>
commit 5a26db5bd25cf4bf32ae9fa9f6136b6b6d5b45c5
Author: Nick Piggin <npiggin@...e.de>
Date:   Wed Jan 16 09:51:58 2008 +0100

    lockdep: fix internal double unlock during self-test
    Lockdep, during self-test (when it was simulating double unlocks) was
    sometimes unconditionally unlocking a spinlock when it had not been
    locked. This won't work for ticket locks.
    
    Signed-off-by: Nick Piggin <npiggin@...e.de>
    Signed-off-by: Ingo Molnar <mingo@...e.hu>
    Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 723bd9f..4335f12 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -2943,9 +2943,10 @@ void lockdep_free_key_range(void *start, unsigned long size)
 	struct list_head *head;
 	unsigned long flags;
 	int i;
+	int locked;
 
 	raw_local_irq_save(flags);
-	graph_lock();
+	locked = graph_lock();
 
 	/*
 	 * Unhash all classes that were created by this module:
@@ -2959,7 +2960,8 @@ void lockdep_free_key_range(void *start, unsigned long size)
 				zap_class(class);
 	}
 
-	graph_unlock();
+	if (locked)
+		graph_unlock();
 	raw_local_irq_restore(flags);
 }
 
@@ -2969,6 +2971,7 @@ void lockdep_reset_lock(struct lockdep_map *lock)
 	struct list_head *head;
 	unsigned long flags;
 	int i, j;
+	int locked;
 
 	raw_local_irq_save(flags);
 
@@ -2987,7 +2990,7 @@ void lockdep_reset_lock(struct lockdep_map *lock)
 	 * Debug check: in the end all mapped classes should
 	 * be gone.
 	 */
-	graph_lock();
+	locked = graph_lock();
 	for (i = 0; i < CLASSHASH_SIZE; i++) {
 		head = classhash_table + i;
 		if (list_empty(head))
@@ -3000,7 +3003,8 @@ void lockdep_reset_lock(struct lockdep_map *lock)
 			}
 		}
 	}
-	graph_unlock();
+	if (locked)
+		graph_unlock();
 
 out_restore:
 	raw_local_irq_restore(flags);
--
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