[PATCH 4/4] drm/xe/bo: add some annotations in bo_put()

[Matthew Brost]

On Tue, Sep 10, 2024 at 04:03:58PM +0100, Matthew Auld wrote:
> On 10/09/2024 15:49, Matthew Brost wrote:
> > On Tue, Sep 10, 2024 at 02:11:49PM +0100, Matthew Auld wrote:
> > > If the put() triggers bo destroy then there is at least one potential
> > > sleeping lock. Also annotate bos_lock and ggtt lock.
> > > 
> > > Signed-off-by: Matthew Auld <matthew.auld at intel.com>
> > > Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray at intel.com>
> > > Cc: Tejas Upadhyay <tejas.upadhyay at intel.com>
> > > Cc: "Thomas Hellström" <thomas.hellstrom at linux.intel.com>
> > > ---
> > >   drivers/gpu/drm/xe/xe_bo.c | 14 ++++++++++++++
> > >   drivers/gpu/drm/xe/xe_bo.h |  6 +-----
> > >   2 files changed, 15 insertions(+), 5 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
> > > index 53948a965404..4176b302c38d 100644
> > > --- a/drivers/gpu/drm/xe/xe_bo.c
> > > +++ b/drivers/gpu/drm/xe/xe_bo.c
> > > @@ -2320,6 +2320,20 @@ void xe_bo_put_commit(struct llist_head *deferred)
> > >   		drm_gem_object_free(&bo->ttm.base.refcount);
> > >   }
> > > +void xe_bo_put(struct xe_bo *bo)
> > > +{
> > > +	might_sleep();
> > > +	if (bo) {
> > > +#ifdef CONFIG_PROC_FS
> > > +		if (bo->client)
> > > +			might_lock(&bo->client->bos_lock);
> > > +#endif
> > > +		if (bo->ggtt_node && bo->ggtt_node->ggtt)
> > > +			might_lock(&bo->ggtt_node->ggtt->lock);
> > 
> > Missed this. We can take dma-resv lock too if we get into the TTM code
> > upon this put too, right? We should probably add that annotate too.
> 
> Yeah, I was also wondering the same thing, but it looks to only be trylock
> in ttm_bo_release(). AFAICT it will only grab the full dma-resv lock from a
> worker, which it does if the lock is contended, or if there are unsignalled
> fences and we need to wait.
> 

Ah ok. I was thinking about this in the path of reclaim, the does
trylocking make it ok to take a dma-resv lock? If it doesn't then I
think we need some sort additional annotation so the final put is not in
the path of reclaim.

Matt

> > 
> > Matt
> > 
> > > +		drm_gem_object_put(&bo->ttm.base);
> > > +	}
> > > +}
> > > +
> > >   /**
> > >    * xe_bo_dumb_create - Create a dumb bo as backing for a fb
> > >    * @file_priv: ...
> > > diff --git a/drivers/gpu/drm/xe/xe_bo.h b/drivers/gpu/drm/xe/xe_bo.h
> > > index dbfb3209615d..6e4be52306df 100644
> > > --- a/drivers/gpu/drm/xe/xe_bo.h
> > > +++ b/drivers/gpu/drm/xe/xe_bo.h
> > > @@ -126,11 +126,7 @@ static inline struct xe_bo *xe_bo_get(struct xe_bo *bo)
> > >   	return bo;
> > >   }
> > > -static inline void xe_bo_put(struct xe_bo *bo)
> > > -{
> > > -	if (bo)
> > > -		drm_gem_object_put(&bo->ttm.base);
> > > -}
> > > +void xe_bo_put(struct xe_bo *bo);
> > >   static inline void __xe_bo_unset_bulk_move(struct xe_bo *bo)
> > >   {
> > > -- 
> > > 2.46.0
> > >