Quoting Tvrtko Ursulin (2019-01-02 13:21:17)
>
> On 02/01/2019 09:41, Chris Wilson wrote:
>
> Give it a bit of commit text please.
A starting point to counter the pervasive struct_mutex. For the goal of
avoiding (or at least blocking under them!) global locks during user
request submission, a simple but important step is being able to manage
each clients GTT separately. For which, we want to replace using the
struct_mutex as the guard for all things GTT/VM and switch instead to a
specific mutex inside i915_address_space.
>
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/i915_gem.c | 14 ++++++++------
> > drivers/gpu/drm/i915/i915_gem_evict.c | 2 ++
> > drivers/gpu/drm/i915/i915_gem_gtt.c | 15 +++++++++++++--
> > drivers/gpu/drm/i915/i915_gem_shrinker.c | 4 ++++
> > drivers/gpu/drm/i915/i915_gem_stolen.c | 2 ++
> > drivers/gpu/drm/i915/i915_vma.c | 11 +++++++++++
> > drivers/gpu/drm/i915/selftests/i915_gem_evict.c | 3 +++
> > drivers/gpu/drm/i915/selftests/i915_gem_gtt.c | 3 +++
> > 8 files changed, 46 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> > index d9e1dcee176c..66445e34c93c 100644
> > --- a/drivers/gpu/drm/i915/i915_gem.c
> > +++ b/drivers/gpu/drm/i915/i915_gem.c
> > @@ -246,18 +246,19 @@ int
> > i915_gem_get_aperture_ioctl(struct drm_device *dev, void *data,
> > struct drm_file *file)
> > {
> > - struct drm_i915_private *dev_priv = to_i915(dev);
> > - struct i915_ggtt *ggtt = &dev_priv->ggtt;
> > + struct i915_ggtt *ggtt = &to_i915(dev)->ggtt;
> > struct drm_i915_gem_get_aperture *args = data;
> > struct i915_vma *vma;
> > u64 pinned;
> >
> > + mutex_lock(&ggtt->vm.mutex);
> > +
> > pinned = ggtt->vm.reserved;
> > - mutex_lock(&dev->struct_mutex);
> > list_for_each_entry(vma, &ggtt->vm.bound_list, vm_link)
> > if (i915_vma_is_pinned(vma))
> > pinned += vma->node.size;
> > - mutex_unlock(&dev->struct_mutex);
> > +
> > + mutex_unlock(&ggtt->vm.mutex);
> >
> > args->aper_size = ggtt->vm.total;
> > args->aper_available_size = args->aper_size - pinned;
> > @@ -1680,20 +1681,21 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
> >
> > static void i915_gem_object_bump_inactive_ggtt(struct drm_i915_gem_object *obj)
> > {
> > - struct drm_i915_private *i915;
> > + struct drm_i915_private *i915 = to_i915(obj->base.dev);
> > struct list_head *list;
> > struct i915_vma *vma;
> >
> > GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));
> >
> > + mutex_lock(&i915->ggtt.vm.mutex);
> > for_each_ggtt_vma(vma, obj) {
> > if (!drm_mm_node_allocated(&vma->node))
> > continue;
> >
> > list_move_tail(&vma->vm_link, &vma->vm->bound_list);
> > }
> > + mutex_unlock(&i915->ggtt.vm.mutex);
> >
> > - i915 = to_i915(obj->base.dev);
> > spin_lock(&i915->mm.obj_lock);
> > list = obj->bind_count ? &i915->mm.bound_list : &i915->mm.unbound_list;
> > list_move_tail(&obj->mm.link, list);
> > diff --git a/drivers/gpu/drm/i915/i915_gem_evict.c b/drivers/gpu/drm/i915/i915_gem_evict.c
> > index 6a3608398d2a..b7c2a396a63f 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_evict.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_evict.c
> > @@ -418,6 +418,7 @@ int i915_gem_evict_vm(struct i915_address_space *vm)
> > }
> >
> > INIT_LIST_HEAD(&eviction_list);
> > + mutex_lock(&vm->mutex);
> > list_for_each_entry(vma, &vm->bound_list, vm_link) {
> > if (i915_vma_is_pinned(vma))
> > continue;
> > @@ -425,6 +426,7 @@ int i915_gem_evict_vm(struct i915_address_space *vm)
> > __i915_vma_pin(vma);
> > list_add(&vma->evict_link, &eviction_list);
> > }
> > + mutex_unlock(&vm->mutex);
> >
> > ret = 0;
> > list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
> > diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > index e5e23c4ac769..7ae10fbb2ee0 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > @@ -1932,7 +1932,10 @@ static struct i915_vma *pd_vma_create(struct gen6_hw_ppgtt *ppgtt, int size)
> > vma->ggtt_view.type = I915_GGTT_VIEW_ROTATED; /* prevent fencing */
> >
> > INIT_LIST_HEAD(&vma->obj_link);
> > +
> > + mutex_lock(&vma->vm->mutex);
> > list_add(&vma->vm_link, &vma->vm->unbound_list);
> > + mutex_unlock(&vma->vm->mutex);
> >
> > return vma;
> > }
> > @@ -3504,9 +3507,10 @@ void i915_gem_restore_gtt_mappings(struct drm_i915_private *dev_priv)
> >
> > i915_check_and_clear_faults(dev_priv);
> >
> > + mutex_lock(&ggtt->vm.mutex);
> > +
> > /* First fill our portion of the GTT with scratch pages */
> > ggtt->vm.clear_range(&ggtt->vm, 0, ggtt->vm.total);
> > -
> > ggtt->vm.closed = true; /* skip rewriting PTE on VMA unbind */
> >
> > /* clflush objects bound into the GGTT and rebind them. */
> > @@ -3516,19 +3520,26 @@ void i915_gem_restore_gtt_mappings(struct drm_i915_private *dev_priv)
> > if (!(vma->flags & I915_VMA_GLOBAL_BIND))
> > continue;
> >
> > + mutex_unlock(&ggtt->vm.mutex);
> > +
> > if (!i915_vma_unbind(vma))
>
> What is the model - traverse under the new lock but then no need to get
> a reference to operate on outside the lock?
>
> > - continue;
> > + goto lock;
> >
> > WARN_ON(i915_vma_bind(vma,
> > obj ? obj->cache_level : 0,
> > PIN_UPDATE));
> > if (obj)
> > WARN_ON(i915_gem_object_set_to_gtt_domain(obj, false));
> > +
> > +lock:
> > + mutex_lock(&ggtt->vm.mutex);
> > }
> >
> > ggtt->vm.closed = false;
> > i915_ggtt_invalidate(dev_priv);
> >
> > + mutex_unlock(&ggtt->vm.mutex);
> > +
> > if (INTEL_GEN(dev_priv) >= 8) {
> > struct intel_ppat *ppat = &dev_priv->ppat;
> >
> > diff --git a/drivers/gpu/drm/i915/i915_gem_shrinker.c b/drivers/gpu/drm/i915/i915_gem_shrinker.c
> > index 95af8cc9fa85..9d04c26c04f9 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_shrinker.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_shrinker.c
> > @@ -490,6 +490,7 @@ i915_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr
> > }
> >
> > /* We also want to clear any cached iomaps as they wrap vmap */
> > + mutex_lock(&i915->ggtt.vm.mutex);
> > list_for_each_entry_safe(vma, next,
> > &i915->ggtt.vm.bound_list, vm_link) {
> > unsigned long count = vma->node.size >> PAGE_SHIFT;
> > @@ -497,9 +498,12 @@ i915_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr
> > if (!vma->iomap || i915_vma_is_active(vma))
> > continue;
> >
> > + mutex_unlock(&i915->ggtt.vm.mutex);
> > if (i915_vma_unbind(vma) == 0)
> > freed_pages += count;
> > + mutex_lock(&i915->ggtt.vm.mutex);
> > }
> > + mutex_unlock(&i915->ggtt.vm.mutex);
> >
> > out:
> > shrinker_unlock(i915, unlock);
> > diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c b/drivers/gpu/drm/i915/i915_gem_stolen.c
> > index 75b97d71f072..21de3a5e9910 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_stolen.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
> > @@ -703,7 +703,9 @@ i915_gem_object_create_stolen_for_preallocated(struct drm_i915_private *dev_priv
> > vma->flags |= I915_VMA_GLOBAL_BIND;
> > __i915_vma_set_map_and_fenceable(vma);
> >
> > + mutex_lock(&ggtt->vm.mutex);
> > list_move_tail(&vma->vm_link, &ggtt->vm.bound_list);
> > + mutex_unlock(&ggtt->vm.mutex);
> >
> > spin_lock(&dev_priv->mm.obj_lock);
> > list_move_tail(&obj->mm.link, &dev_priv->mm.bound_list);
> > diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
> > index 7de28baffb8f..dcbd0d345c72 100644
> > --- a/drivers/gpu/drm/i915/i915_vma.c
> > +++ b/drivers/gpu/drm/i915/i915_vma.c
> > @@ -213,7 +213,10 @@ vma_create(struct drm_i915_gem_object *obj,
> > }
> > rb_link_node(&vma->obj_node, rb, p);
> > rb_insert_color(&vma->obj_node, &obj->vma_tree);
> > +
> > + mutex_lock(&vm->mutex);
> > list_add(&vma->vm_link, &vm->unbound_list);
> > + mutex_unlock(&vm->mutex);
> >
> > return vma;
> >
> > @@ -656,7 +659,9 @@ i915_vma_insert(struct i915_vma *vma, u64 size, u64 alignment, u64 flags)
> > GEM_BUG_ON(!drm_mm_node_allocated(&vma->node));
> > GEM_BUG_ON(!i915_gem_valid_gtt_space(vma, cache_level));
> >
> > + mutex_lock(&vma->vm->mutex);
> > list_move_tail(&vma->vm_link, &vma->vm->bound_list);
> > + mutex_unlock(&vma->vm->mutex);
> >
> > if (vma->obj) {
> > struct drm_i915_gem_object *obj = vma->obj;
> > @@ -689,8 +694,10 @@ i915_vma_remove(struct i915_vma *vma)
> >
> > vma->ops->clear_pages(vma);
> >
> > + mutex_lock(&vma->vm->mutex);
> > drm_mm_remove_node(&vma->node);
> > list_move_tail(&vma->vm_link, &vma->vm->unbound_list);
> > + mutex_unlock(&vma->vm->mutex);
> >
> > /*
> > * Since the unbound list is global, only move to that list if
> > @@ -802,7 +809,11 @@ static void __i915_vma_destroy(struct i915_vma *vma)
> > GEM_BUG_ON(i915_gem_active_isset(&vma->last_fence));
> >
> > list_del(&vma->obj_link);
> > +
> > + mutex_lock(&vma->vm->mutex);
> > list_del(&vma->vm_link);
> > + mutex_unlock(&vma->vm->mutex);
> > +
> > if (vma->obj)
> > rb_erase(&vma->obj_node, &vma->obj->vma_tree);
> >
> > diff --git a/drivers/gpu/drm/i915/selftests/i915_gem_evict.c b/drivers/gpu/drm/i915/selftests/i915_gem_evict.c
> > index 9d0fe8aac219..eaefba7470f7 100644
> > --- a/drivers/gpu/drm/i915/selftests/i915_gem_evict.c
> > +++ b/drivers/gpu/drm/i915/selftests/i915_gem_evict.c
> > @@ -67,10 +67,13 @@ static int populate_ggtt(struct drm_i915_private *i915)
> >
> > static void unpin_ggtt(struct drm_i915_private *i915)
> > {
> > + struct i915_ggtt *ggtt = &i915->ggtt;
> > struct i915_vma *vma;
> >
> > + mutex_lock(&ggtt->vm.mutex);
> > list_for_each_entry(vma, &i915->ggtt.vm.bound_list, vm_link)
> > i915_vma_unpin(vma);
> > + mutex_unlock(&ggtt->vm.mutex);
> > }
> >
> > static void cleanup_objects(struct drm_i915_private *i915)
> > diff --git a/drivers/gpu/drm/i915/selftests/i915_gem_gtt.c b/drivers/gpu/drm/i915/selftests/i915_gem_gtt.c
> > index 18db008c0c62..850f9eff6029 100644
> > --- a/drivers/gpu/drm/i915/selftests/i915_gem_gtt.c
> > +++ b/drivers/gpu/drm/i915/selftests/i915_gem_gtt.c
> > @@ -1237,7 +1237,10 @@ static void track_vma_bind(struct i915_vma *vma)
> > __i915_gem_object_pin_pages(obj);
> >
> > vma->pages = obj->mm.pages;
> > +
> > + mutex_lock(&vma->vm->mutex);
> > list_move_tail(&vma->vm_link, &vma->vm->bound_list);
> > + mutex_unlock(&vma->vm->mutex);
> > }
> >
> > static int exercise_mock(struct drm_i915_private *i915,
> >
>
> Why a mutex? Will there be sleeping under it in subsequent patches?
Yeah, we will need to have a wait on GPU under a mutex at some point.
And this is the most likely candidate. Those patches are a bit scarier
and at the last check not deadlock free yet; I think it may need a few
different rules.
-Chris
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