On Sat, Jun 15, 2019 at 07:14:35AM -0700, Christoph Hellwig wrote:
> > mutex_lock(&hmm->lock);
> > - list_for_each_entry(range, &hmm->ranges, list)
> > - range->valid = false;
> > - wake_up_all(&hmm->wq);
> > + /*
> > + * Since hmm_range_register() holds the mmget() lock hmm_release() is
> > + * prevented as long as a range exists.
> > + */
> > + WARN_ON(!list_empty(&hmm->ranges));
> > mutex_unlock(&hmm->lock);
>
> This can just use list_empty_careful and avoid the lock entirely.
Sure, it is just a debugging helper and the mmput should serialize
thinigs enough to be reliable. I had to move the RCU patch ahead of
this. Thanks
diff --git a/mm/hmm.c b/mm/hmm.c
index a9ace28984ea42..1eddda45cefae7 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -124,13 +124,11 @@ static void hmm_release(struct mmu_notifier *mn, struct
mm_struct *mm)
if (!kref_get_unless_zero(&hmm->kref))
return;
- mutex_lock(&hmm->lock);
/*
* Since hmm_range_register() holds the mmget() lock hmm_release() is
* prevented as long as a range exists.
*/
- WARN_ON(!list_empty(&hmm->ranges));
- mutex_unlock(&hmm->lock);
+ WARN_ON(!list_empty_careful(&hmm->ranges));
down_write(&hmm->mirrors_sem);
mirror = list_first_entry_or_null(&hmm->mirrors, struct hmm_mirror,
@@ -938,7 +936,7 @@ void hmm_range_unregister(struct hmm_range *range)
return;
mutex_lock(&hmm->lock);
- list_del(&range->list);
+ list_del_init(&range->list);
mutex_unlock(&hmm->lock);
/* Drop reference taken by hmm_range_register() */
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