Re: [PATCH 2/4] mm, notifier: Prime lockdep

[Jason Gunthorpe]

On Tue, Aug 20, 2019 at 10:19:00AM +0200, Daniel Vetter wrote:
> We want to teach lockdep that mmu notifiers can be called from direct
> reclaim paths, since on many CI systems load might never reach that
> level (e.g. when just running fuzzer or small functional tests).
> 
> Motivated by a discussion with Jason.
> 
> I've put the annotation into mmu_notifier_register since only when we
> have mmu notifiers registered is there any point in teaching lockdep
> about them. Also, we already have a kmalloc(, GFP_KERNEL), so this is
> safe.
> 
> Cc: Jason Gunthorpe 
> Cc: Chris Wilson 
> Cc: Andrew Morton 
> Cc: David Rientjes 
> Cc: "Jérôme Glisse" 
> Cc: Michal Hocko 
> Cc: "Christian König" 
> Cc: Greg Kroah-Hartman 
> Cc: Daniel Vetter 
> Cc: Mike Rapoport 
> Cc: linux...@kvack.org
> Signed-off-by: Daniel Vetter 
>  mm/mmu_notifier.c | 7 +++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
> index d12e3079e7a4..538d3bb87f9b 100644
> +++ b/mm/mmu_notifier.c
> @@ -256,6 +256,13 @@ static int do_mmu_notifier_register(struct mmu_notifier 
> *mn,
>  
>   BUG_ON(atomic_read(>mm_users) <= 0);
>  
> + if (IS_ENABLED(CONFIG_LOCKDEP)) {
> + fs_reclaim_acquire(GFP_KERNEL);
> + lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
> + lock_map_release(&__mmu_notifier_invalidate_range_start_map);
> + fs_reclaim_release(GFP_KERNEL);
> + }

Lets try it out at least

Reviewed-by: Jason Gunthorpe 

Jason

[PATCH 2/4] mm, notifier: Prime lockdep

[Daniel Vetter]

We want to teach lockdep that mmu notifiers can be called from direct
reclaim paths, since on many CI systems load might never reach that
level (e.g. when just running fuzzer or small functional tests).

Motivated by a discussion with Jason.

I've put the annotation into mmu_notifier_register since only when we
have mmu notifiers registered is there any point in teaching lockdep
about them. Also, we already have a kmalloc(, GFP_KERNEL), so this is
safe.

Cc: Jason Gunthorpe 
Cc: Chris Wilson 
Cc: Andrew Morton 
Cc: David Rientjes 
Cc: "Jérôme Glisse" 
Cc: Michal Hocko 
Cc: "Christian König" 
Cc: Greg Kroah-Hartman 
Cc: Daniel Vetter 
Cc: Mike Rapoport 
Cc: linux...@kvack.org
Signed-off-by: Daniel Vetter 
---
 mm/mmu_notifier.c | 7 +++
 1 file changed, 7 insertions(+)

diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index d12e3079e7a4..538d3bb87f9b 100644
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -256,6 +256,13 @@ static int do_mmu_notifier_register(struct mmu_notifier 
*mn,
 
BUG_ON(atomic_read(>mm_users) <= 0);
 
+   if (IS_ENABLED(CONFIG_LOCKDEP)) {
+   fs_reclaim_acquire(GFP_KERNEL);
+   lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
+   lock_map_release(&__mmu_notifier_invalidate_range_start_map);
+   fs_reclaim_release(GFP_KERNEL);
+   }
+
ret = -ENOMEM;
mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm), GFP_KERNEL);
if (unlikely(!mmu_notifier_mm))
-- 
2.23.0.rc1

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