Takashi Iwai <tiwai@xxxxxxx> wrote:
> =======================================================
> [ INFO: possible circular locking dependency detected ]
> 2.6.30-test #7
> -------------------------------------------------------
> swapper/0 is trying to acquire lock:
> (&cwq->lock){-.-...}, at: [<c01519f3>] __queue_work+0x1f/0x4e
>
> but task is already holding lock:
> (&q->lock){-.-.-.}, at: [<c012cc9c>] __wake_up+0x26/0x5c
>
> which lock already depends on the new lock.
> ...
Can you try the attached patch from Peter Zijlstra? It should cause the work
queue's waitqueue spinlock to have a separate lockdep class from the page
bit's waitqueue.
David
---
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Subject: [PATCH] Give waitqueue spinlocks their own lockdep classes
Give waitqueue spinlocks their own lockdep classes when they are initialised
from init_waitqueue_head(). This means that struct wait_queue::func functions
can operate other waitqueues.
This is used by CacheFiles to catch the page from a backing fs being unlocked
and to wake up another thread to take a copy of it.
---
include/linux/wait.h | 9 ++++++++-
kernel/wait.c | 5 +++--
2 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/include/linux/wait.h b/include/linux/wait.h
index 6788e1a..cf3c2f5 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -77,7 +77,14 @@ struct task_struct;
#define __WAIT_BIT_KEY_INITIALIZER(word, bit) \
{ .flags = word, .bit_nr = bit, }
-extern void init_waitqueue_head(wait_queue_head_t *q);
+extern void __init_waitqueue_head(wait_queue_head_t *q, struct lock_class_key *);
+
+#define init_waitqueue_head(q) \
+ do { \
+ static struct lock_class_key __key; \
+ \
+ __init_waitqueue_head((q), &__key); \
+ } while (0)
#ifdef CONFIG_LOCKDEP
# define __WAIT_QUEUE_HEAD_INIT_ONSTACK(name) \
diff --git a/kernel/wait.c b/kernel/wait.c
index ea7c3b4..c4bd3d8 100644
--- a/kernel/wait.c
+++ b/kernel/wait.c
@@ -10,13 +10,14 @@
#include <linux/wait.h>
#include <linux/hash.h>
-void init_waitqueue_head(wait_queue_head_t *q)
+void __init_waitqueue_head(wait_queue_head_t *q, struct lock_class_key *key)
{
spin_lock_init(&q->lock);
+ lockdep_set_class(&q->lock, key);
INIT_LIST_HEAD(&q->task_list);
}
-EXPORT_SYMBOL(init_waitqueue_head);
+EXPORT_SYMBOL(__init_waitqueue_head);
void add_wait_queue(wait_queue_head_t *q, wait_queue_t *wait)
{
--
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