On Tue, 2021-03-23 at 16:18 +0000, Matthew Auld wrote:
> On Tue, 23 Mar 2021 at 15:52, Maarten Lankhorst
> <maarten.lankhorst@xxxxxxxxxxxxxxx> wrote:
> >
> > From: Thomas Hellström <thomas.hellstrom@xxxxxxxxx>
> >
> > Stolen objects need to lock, and we may call put_pages when
> > refcount drops to 0, ensure all calls are handled correctly.
> >
> > Changes since v1:
> > - Rebase on top of upstream changes.
> >
> > Idea-from: Thomas Hellström <thomas.hellstrom@xxxxxxxxx>
> > Signed-off-by: Maarten Lankhorst
> > <maarten.lankhorst@xxxxxxxxxxxxxxx>
> > Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/gem/i915_gem_object.h | 14 ++++++++++++++
> > drivers/gpu/drm/i915/gem/i915_gem_pages.c | 14 ++++++++++++--
> > drivers/gpu/drm/i915/gem/i915_gem_stolen.c | 12 +++++++-----
> > 3 files changed, 33 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h
> > b/drivers/gpu/drm/i915/gem/i915_gem_object.h
> > index 983f2d4b2a85..74de195b57de 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
> > @@ -144,6 +144,20 @@ i915_gem_object_put(struct drm_i915_gem_object
> > *obj)
> >
> > #define assert_object_held(obj) dma_resv_assert_held((obj)-
> > >base.resv)
> >
> > +/*
> > + * If more than one potential simultaneous locker, assert held.
> > + */
> > +static inline void assert_object_held_shared(struct
> > drm_i915_gem_object *obj)
> > +{
> > + /*
> > + * Note mm list lookup is protected by
>
> What is meant with mm list here? Maybe just a stale comment?
That would be the i915->mm lists, (shrink and purge).
>
> > + * kref_get_unless_zero().
> > + */
> > + if (IS_ENABLED(CONFIG_LOCKDEP) &&
> > + kref_read(&obj->base.refcount) > 0)
> > + lockdep_assert_held(&obj->mm.lock);
> > +}
> > +
> > static inline int __i915_gem_object_lock(struct
> > drm_i915_gem_object *obj,
> > struct i915_gem_ww_ctx
> > *ww,
> > bool intr)
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> > b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> > index a24617af3c93..2d0065fa6e80 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> > @@ -19,7 +19,7 @@ void __i915_gem_object_set_pages(struct
> > drm_i915_gem_object *obj,
> > bool shrinkable;
> > int i;
> >
> > - lockdep_assert_held(&obj->mm.lock);
> > + assert_object_held_shared(obj);
> >
> > if (i915_gem_object_is_volatile(obj))
> > obj->mm.madv = I915_MADV_DONTNEED;
> > @@ -70,6 +70,7 @@ void __i915_gem_object_set_pages(struct
> > drm_i915_gem_object *obj,
> > struct list_head *list;
> > unsigned long flags;
> >
> > + lockdep_assert_held(&obj->mm.lock);
> > spin_lock_irqsave(&i915->mm.obj_lock, flags);
> >
> > i915->mm.shrink_count++;
> > @@ -91,6 +92,8 @@ int ____i915_gem_object_get_pages(struct
> > drm_i915_gem_object *obj)
> > struct drm_i915_private *i915 = to_i915(obj->base.dev);
> > int err;
> >
> > + assert_object_held_shared(obj);
> > +
> > if (unlikely(obj->mm.madv != I915_MADV_WILLNEED)) {
> > drm_dbg(&i915->drm,
> > "Attempting to obtain a purgeable
> > object\n");
> > @@ -118,6 +121,8 @@ int __i915_gem_object_get_pages(struct
> > drm_i915_gem_object *obj)
> > if (err)
> > return err;
> >
> > + assert_object_held_shared(obj);
> > +
> > if (unlikely(!i915_gem_object_has_pages(obj))) {
> > GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
> >
> > @@ -145,7 +150,7 @@ void i915_gem_object_truncate(struct
> > drm_i915_gem_object *obj)
> > /* Try to discard unwanted pages */
> > void i915_gem_object_writeback(struct drm_i915_gem_object *obj)
> > {
> > - lockdep_assert_held(&obj->mm.lock);
> > + assert_object_held_shared(obj);
> > GEM_BUG_ON(i915_gem_object_has_pages(obj));
> >
> > if (obj->ops->writeback)
> > @@ -176,6 +181,8 @@ __i915_gem_object_unset_pages(struct
> > drm_i915_gem_object *obj)
> > {
> > struct sg_table *pages;
> >
> > + assert_object_held_shared(obj);
> > +
> > pages = fetch_and_zero(&obj->mm.pages);
> > if (IS_ERR_OR_NULL(pages))
> > return pages;
> > @@ -203,6 +210,9 @@ int __i915_gem_object_put_pages_locked(struct
> > drm_i915_gem_object *obj)
> > if (i915_gem_object_has_pinned_pages(obj))
> > return -EBUSY;
> >
> > + /* May be called by shrinker from within get_pages() (on
> > another bo) */
> > + assert_object_held_shared(obj);
> > +
> > i915_gem_object_release_mmap_offset(obj);
> >
> > /*
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
> > b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
> > index 7cdb32d881d9..b0597de206de 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
> > @@ -637,13 +637,15 @@ static int
> > __i915_gem_object_create_stolen(struct intel_memory_region *mem,
> > cache_level = HAS_LLC(mem->i915) ? I915_CACHE_LLC :
> > I915_CACHE_NONE;
> > i915_gem_object_set_cache_coherency(obj, cache_level);
> >
> > - err = i915_gem_object_pin_pages(obj);
> > - if (err)
> > - return err;
> > + if (WARN_ON(!i915_gem_object_trylock(obj)))
> > + return -EBUSY;
> >
> > - i915_gem_object_init_memory_region(obj, mem);
> > + err = i915_gem_object_pin_pages(obj);
> > + if (!err)
> > + i915_gem_object_init_memory_region(obj, mem);
>
> Probably more consistent to call init_memory_region() before calling
> pin_pages(), but I guess it was already like that, plus it doesn't
> seem to matter for stolen memory.
Yes, I agree, Probably a rebasing error? In the DG1 enabling code we
add the object to the relevant region mm lists during get_pages(), and
to do that the region needs to be initialized.
/Thomas
>
> Reviewed-by: Matthew Auld <matthew.auld@xxxxxxxxx>
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