[Intel-gfx] [PATCH v9 17/70] drm/i915: Flatten obj->mm.lock
Daniel Vetter
daniel at ffwll.ch
Wed Mar 24 11:13:49 UTC 2021
On Tue, Mar 23, 2021 at 04:50:06PM +0100, Maarten Lankhorst wrote:
> With userptr fixed, there is no need for all separate lockdep classes
> now, and we can remove all lockdep tricks used. A trylock in the
> shrinker is all we need now to flatten the locking hierarchy.
>
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Reviewed-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
Minor conflict with this one here when applying, due to lack of
https://lore.kernel.org/intel-gfx/20210202154318.19246-1-chris@chris-wilson.co.
It's not a bad idea, but if we do this we really should move this helper
into the right headers, and ideally get linux-mm/-fs folks to ack this as
a good idea. Especially Dave Chinner very much wants to be in the loop for
anything that touches fs_reclaim lockdep annotations.
-Daniel
> ---
> drivers/gpu/drm/i915/gem/i915_gem_object.c | 5 +--
> drivers/gpu/drm/i915/gem/i915_gem_object.h | 20 ++----------
> drivers/gpu/drm/i915/gem/i915_gem_pages.c | 34 ++++++++++----------
> drivers/gpu/drm/i915/gem/i915_gem_phys.c | 2 +-
> drivers/gpu/drm/i915/gem/i915_gem_shrinker.c | 10 +++---
> drivers/gpu/drm/i915/gem/i915_gem_userptr.c | 2 +-
> 6 files changed, 27 insertions(+), 46 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c b/drivers/gpu/drm/i915/gem/i915_gem_object.c
> index 6083b9c14be6..821cb40f8d73 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_object.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c
> @@ -62,7 +62,7 @@ void i915_gem_object_init(struct drm_i915_gem_object *obj,
> const struct drm_i915_gem_object_ops *ops,
> struct lock_class_key *key, unsigned flags)
> {
> - __mutex_init(&obj->mm.lock, ops->name ?: "obj->mm.lock", key);
> + mutex_init(&obj->mm.lock);
>
> spin_lock_init(&obj->vma.lock);
> INIT_LIST_HEAD(&obj->vma.list);
> @@ -86,9 +86,6 @@ void i915_gem_object_init(struct drm_i915_gem_object *obj,
> mutex_init(&obj->mm.get_page.lock);
> INIT_RADIX_TREE(&obj->mm.get_dma_page.radix, GFP_KERNEL | __GFP_NOWARN);
> mutex_init(&obj->mm.get_dma_page.lock);
> -
> - if (IS_ENABLED(CONFIG_LOCKDEP) && i915_gem_object_is_shrinkable(obj))
> - fs_reclaim_taints_mutex(&obj->mm.lock);
> }
>
> /**
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h
> index b5af9c440ac5..a0e1c4ff0de4 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
> @@ -372,27 +372,10 @@ void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
> int ____i915_gem_object_get_pages(struct drm_i915_gem_object *obj);
> int __i915_gem_object_get_pages(struct drm_i915_gem_object *obj);
>
> -enum i915_mm_subclass { /* lockdep subclass for obj->mm.lock/struct_mutex */
> - I915_MM_NORMAL = 0,
> - /*
> - * Only used by struct_mutex, when called "recursively" from
> - * direct-reclaim-esque. Safe because there is only every one
> - * struct_mutex in the entire system.
> - */
> - I915_MM_SHRINKER = 1,
> - /*
> - * Used for obj->mm.lock when allocating pages. Safe because the object
> - * isn't yet on any LRU, and therefore the shrinker can't deadlock on
> - * it. As soon as the object has pages, obj->mm.lock nests within
> - * fs_reclaim.
> - */
> - I915_MM_GET_PAGES = 1,
> -};
> -
> static inline int __must_check
> i915_gem_object_pin_pages(struct drm_i915_gem_object *obj)
> {
> - might_lock_nested(&obj->mm.lock, I915_MM_GET_PAGES);
> + might_lock(&obj->mm.lock);
>
> if (atomic_inc_not_zero(&obj->mm.pages_pin_count))
> return 0;
> @@ -436,6 +419,7 @@ i915_gem_object_unpin_pages(struct drm_i915_gem_object *obj)
> }
>
> int __i915_gem_object_put_pages(struct drm_i915_gem_object *obj);
> +int __i915_gem_object_put_pages_locked(struct drm_i915_gem_object *obj);
> void i915_gem_object_truncate(struct drm_i915_gem_object *obj);
> void i915_gem_object_writeback(struct drm_i915_gem_object *obj);
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> index e7d7650072c5..e947d4c0da1f 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> @@ -114,7 +114,7 @@ int __i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
> {
> int err;
>
> - err = mutex_lock_interruptible_nested(&obj->mm.lock, I915_MM_GET_PAGES);
> + err = mutex_lock_interruptible(&obj->mm.lock);
> if (err)
> return err;
>
> @@ -196,21 +196,13 @@ __i915_gem_object_unset_pages(struct drm_i915_gem_object *obj)
> return pages;
> }
>
> -int __i915_gem_object_put_pages(struct drm_i915_gem_object *obj)
> +int __i915_gem_object_put_pages_locked(struct drm_i915_gem_object *obj)
> {
> struct sg_table *pages;
> - int err;
>
> if (i915_gem_object_has_pinned_pages(obj))
> return -EBUSY;
>
> - /* May be called by shrinker from within get_pages() (on another bo) */
> - mutex_lock(&obj->mm.lock);
> - if (unlikely(atomic_read(&obj->mm.pages_pin_count))) {
> - err = -EBUSY;
> - goto unlock;
> - }
> -
> i915_gem_object_release_mmap_offset(obj);
>
> /*
> @@ -226,14 +218,22 @@ int __i915_gem_object_put_pages(struct drm_i915_gem_object *obj)
> * get_pages backends we should be better able to handle the
> * cancellation of the async task in a more uniform manner.
> */
> - if (!pages)
> - pages = ERR_PTR(-EINVAL);
> -
> - if (!IS_ERR(pages))
> + if (!IS_ERR_OR_NULL(pages))
> obj->ops->put_pages(obj, pages);
>
> - err = 0;
> -unlock:
> + return 0;
> +}
> +
> +int __i915_gem_object_put_pages(struct drm_i915_gem_object *obj)
> +{
> + int err;
> +
> + if (i915_gem_object_has_pinned_pages(obj))
> + return -EBUSY;
> +
> + /* May be called by shrinker from within get_pages() (on another bo) */
> + mutex_lock(&obj->mm.lock);
> + err = __i915_gem_object_put_pages_locked(obj);
> mutex_unlock(&obj->mm.lock);
>
> return err;
> @@ -341,7 +341,7 @@ void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj,
> !i915_gem_object_type_has(obj, I915_GEM_OBJECT_HAS_IOMEM))
> return ERR_PTR(-ENXIO);
>
> - err = mutex_lock_interruptible_nested(&obj->mm.lock, I915_MM_GET_PAGES);
> + err = mutex_lock_interruptible(&obj->mm.lock);
> if (err)
> return ERR_PTR(err);
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_phys.c b/drivers/gpu/drm/i915/gem/i915_gem_phys.c
> index 06c481ff79d8..44329c435cf1 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_phys.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_phys.c
> @@ -236,7 +236,7 @@ int i915_gem_object_attach_phys(struct drm_i915_gem_object *obj, int align)
> if (err)
> return err;
>
> - err = mutex_lock_interruptible_nested(&obj->mm.lock, I915_MM_GET_PAGES);
> + err = mutex_lock_interruptible(&obj->mm.lock);
> if (err)
> goto err_unlock;
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c b/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c
> index b64a0788381f..3052ef5ad89d 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c
> @@ -49,9 +49,9 @@ static bool unsafe_drop_pages(struct drm_i915_gem_object *obj,
> flags = I915_GEM_OBJECT_UNBIND_TEST;
>
> if (i915_gem_object_unbind(obj, flags) == 0)
> - __i915_gem_object_put_pages(obj);
> + return true;
>
> - return !i915_gem_object_has_pages(obj);
> + return false;
> }
>
> static void try_to_writeback(struct drm_i915_gem_object *obj,
> @@ -200,10 +200,10 @@ i915_gem_shrink(struct drm_i915_private *i915,
>
> spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
>
> - if (unsafe_drop_pages(obj, shrink)) {
> + if (unsafe_drop_pages(obj, shrink) &&
> + mutex_trylock(&obj->mm.lock)) {
> /* May arrive from get_pages on another bo */
> - mutex_lock(&obj->mm.lock);
> - if (!i915_gem_object_has_pages(obj)) {
> + if (!__i915_gem_object_put_pages_locked(obj)) {
> try_to_writeback(obj, shrink);
> count += obj->base.size >> PAGE_SHIFT;
> }
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> index 1e42fbc68697..503325e74eff 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> @@ -253,7 +253,7 @@ static int i915_gem_object_userptr_unbind(struct drm_i915_gem_object *obj, bool
> if (GEM_WARN_ON(i915_gem_object_has_pinned_pages(obj)))
> return -EBUSY;
>
> - mutex_lock_nested(&obj->mm.lock, I915_MM_GET_PAGES);
> + mutex_lock(&obj->mm.lock);
>
> pages = __i915_gem_object_unset_pages(obj);
> if (!IS_ERR_OR_NULL(pages))
> --
> 2.31.0
>
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--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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