On Tue, 2009-08-04 at 16:50 +0100, David Howells wrote:
> Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> > Creating a new class for your second workqueue might help,
>
> I only have one workqueue. The problem is there are two waitqueues, but
> init_waitqueue_head() always sets q->lock to the same class.
Ah, right, I read it backwards then.
> > we'd have to pass a second key through __create_workqueue_key() and pass
> > that into init_cpu_workqueue() and apply it to cwq->lock using
> > lockdep_set_class() and co.
>
> Actually, wouldn't just making init_cpu_workqueue() apply a class to
> cwq->more_work that's common to all workqueues suffice?
That's the default behaviour.
> Or even, have
> init_waitqueue_head() apply an alternate class to q->lock?
Right, that would work. Something akin to all the other per instance
classes would do I guess.
Utterly untested..
---
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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