Re: [Intel-gfx] [PATCH v9 32/70] drm/i915: Prepare for obj->mm.lock removal, v2.

On Tue, 23 Mar 2021 at 15:52, Maarten Lankhorst maarten.lankhorst@linux.intel.com wrote:

From: Thomas Hellström thomas.hellstrom@intel.com

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@intel.com Signed-off-by: Maarten Lankhorst maarten.lankhorst@linux.intel.com Signed-off-by: Thomas Hellström thomas.hellstrom@linux.intel.com

---

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?

•    * 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.

Reviewed-by: Matthew Auld matthew.auld@intel.com